Bonjour
J'ai parcouru beaucoup de post depuis ce matin, sans trouver remède à mon problème, et me permets de vous solliciter.
Sur vieux portable ACER TRavelMate TM8331-742G16n (2 Go de Ram, 1,3 GHz), j'avais le wifi sous Windows 10. Je viens de passer à Xubuntu 18.04 et plus de wifi. Cette absence de wifi est constatée après l'installation sans les mises à jour et également après les mises à jour. Voilà les données demandées: 
lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 18.04.5 LTS
Release:	18.04
Codename:	bionic

lsusb
Bus 002 Device 002: ID 1c7a:0801 LighTuning Technology Inc. Fingerprint Reader
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 008 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 002: ID 04f2:b19d Chicony Electronics Co., Ltd 
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub

lspci
00:00.0 Host bridge: Intel Corporation Mobile 4 Series Chipset Memory Controller Hub (rev 07)
00:02.0 VGA compatible controller: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller (rev 07)
00:02.1 Display controller: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller (rev 07)
00:1a.0 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #4 (rev 03)
00:1a.1 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #5 (rev 03)
00:1a.7 USB controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #2 (rev 03)
00:1b.0 Audio device: Intel Corporation 82801I (ICH9 Family) HD Audio Controller (rev 03)
00:1c.0 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 1 (rev 03)
00:1c.2 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 3 (rev 03)
00:1d.0 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #1 (rev 03)
00:1d.1 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #2 (rev 03)
00:1d.2 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #3 (rev 03)
00:1d.3 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #6 (rev 03)
00:1d.7 USB controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #1 (rev 03)
00:1e.0 PCI bridge: Intel Corporation 82801 Mobile PCI Bridge (rev 93)
00:1f.0 ISA bridge: Intel Corporation ICH9M-E LPC Interface Controller (rev 03)
00:1f.2 SATA controller: Intel Corporation 82801IBM/IEM (ICH9M/ICH9M-E) 4 port SATA Controller [AHCI mode] (rev 03)
00:1f.3 SMBus: Intel Corporation 82801I (ICH9 Family) SMBus Controller (rev 03)
00:1f.6 Signal processing controller: Intel Corporation 82801I (ICH9 Family) Thermal Subsystem (rev 03)
01:00.0 Network controller: Intel Corporation Centrino Wireless-N 1000 [Condor Peak]
02:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 02)

lspci -k -nn | grep -A 3 -i net
01:00.0 Network controller [0280]: Intel Corporation Centrino Wireless-N 1000 [Condor Peak] [8086:0083]
	Subsystem: Intel Corporation Centrino Wireless-N 1000 BGN [8086:1305]
	Kernel driver in use: iwlwifi
	Kernel modules: iwlwifi
02:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller [10ec:8168] (rev 02)
	Subsystem: Acer Incorporated [ALI] RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller [1025:0283]
	Kernel driver in use: r8169
	Kernel modules: r8169

lspci -k
00:00.0 Host bridge: Intel Corporation Mobile 4 Series Chipset Memory Controller Hub (rev 07)
	Subsystem: Acer Incorporated [ALI] Mobile 4 Series Chipset Memory Controller Hub
00:02.0 VGA compatible controller: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller (rev 07)
	Subsystem: Acer Incorporated [ALI] Mobile 4 Series Chipset Integrated Graphics Controller
	Kernel driver in use: i915
	Kernel modules: i915
00:02.1 Display controller: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller (rev 07)
	Subsystem: Acer Incorporated [ALI] Mobile 4 Series Chipset Integrated Graphics Controller
00:1a.0 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #4 (rev 03)
	Subsystem: Acer Incorporated [ALI] 82801I (ICH9 Family) USB UHCI Controller
	Kernel driver in use: uhci_hcd
00:1a.1 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #5 (rev 03)
	Subsystem: Acer Incorporated [ALI] 82801I (ICH9 Family) USB UHCI Controller
	Kernel driver in use: uhci_hcd
00:1a.7 USB controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #2 (rev 03)
	Subsystem: Acer Incorporated [ALI] 82801I (ICH9 Family) USB2 EHCI Controller
	Kernel driver in use: ehci-pci
00:1b.0 Audio device: Intel Corporation 82801I (ICH9 Family) HD Audio Controller (rev 03)
	Subsystem: Acer Incorporated [ALI] 82801I (ICH9 Family) HD Audio Controller
	Kernel driver in use: snd_hda_intel
	Kernel modules: snd_hda_intel
00:1c.0 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 1 (rev 03)
	Kernel driver in use: pcieport
00:1c.2 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 3 (rev 03)
	Kernel driver in use: pcieport
00:1d.0 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #1 (rev 03)
	Subsystem: Acer Incorporated [ALI] 82801I (ICH9 Family) USB UHCI Controller
	Kernel driver in use: uhci_hcd
00:1d.1 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #2 (rev 03)
	Subsystem: Acer Incorporated [ALI] 82801I (ICH9 Family) USB UHCI Controller
	Kernel driver in use: uhci_hcd
00:1d.2 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #3 (rev 03)
	Subsystem: Acer Incorporated [ALI] 82801I (ICH9 Family) USB UHCI Controller
	Kernel driver in use: uhci_hcd
00:1d.3 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #6 (rev 03)
	Subsystem: Acer Incorporated [ALI] 82801I (ICH9 Family) USB UHCI Controller
	Kernel driver in use: uhci_hcd
00:1d.7 USB controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #1 (rev 03)
	Subsystem: Acer Incorporated [ALI] 82801I (ICH9 Family) USB2 EHCI Controller
	Kernel driver in use: ehci-pci
00:1e.0 PCI bridge: Intel Corporation 82801 Mobile PCI Bridge (rev 93)
00:1f.0 ISA bridge: Intel Corporation ICH9M-E LPC Interface Controller (rev 03)
	Subsystem: Acer Incorporated [ALI] ICH9M-E LPC Interface Controller
	Kernel driver in use: lpc_ich
	Kernel modules: lpc_ich
00:1f.2 SATA controller: Intel Corporation 82801IBM/IEM (ICH9M/ICH9M-E) 4 port SATA Controller [AHCI mode] (rev 03)
	Subsystem: Acer Incorporated [ALI] 82801IBM/IEM (ICH9M/ICH9M-E) 4 port SATA Controller [AHCI mode]
	Kernel driver in use: ahci
	Kernel modules: ahci
00:1f.3 SMBus: Intel Corporation 82801I (ICH9 Family) SMBus Controller (rev 03)
	Subsystem: Acer Incorporated [ALI] 82801I (ICH9 Family) SMBus Controller
	Kernel modules: i2c_i801
00:1f.6 Signal processing controller: Intel Corporation 82801I (ICH9 Family) Thermal Subsystem (rev 03)
	Subsystem: Acer Incorporated [ALI] 82801I (ICH9 Family) Thermal Subsystem
01:00.0 Network controller: Intel Corporation Centrino Wireless-N 1000 [Condor Peak]
	Subsystem: Intel Corporation Centrino Wireless-N 1000 BGN
	Kernel driver in use: iwlwifi
	Kernel modules: iwlwifi
02:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 02)
	Subsystem: Acer Incorporated [ALI] RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
	Kernel driver in use: r8169
	Kernel modules: r8169

sudo lshw -C network
[sudo] Mot de passe de tin : 
  *-network DÉSACTIVÉ       
       description: Interface réseau sans fil
       produit: Centrino Wireless-N 1000 [Condor Peak]
       fabriquant: Intel Corporation
       identifiant matériel: 0
       information bus: pci@0000:01:00.0
       nom logique: wlp1s0
       version: 00
       numéro de série: 00:26:c7:57:54:8e
       bits: 64 bits
       horloge: 33MHz
       fonctionnalités: pm msi pciexpress bus_master cap_list ethernet physical wireless
       configuration: broadcast=yes driver=iwlwifi driverversion=5.4.0-62-generic firmware=39.31.5.1 build 35138 latency=0 link=no multicast=yes wireless=IEEE 802.11
       ressources: irq:28 mémoire:a3500000-a3501fff
  *-network
       description: Ethernet interface
       produit: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
       fabriquant: Realtek Semiconductor Co., Ltd.
       identifiant matériel: 0
       information bus: pci@0000:02:00.0
       nom logique: enp2s0
       version: 02
       numéro de série: 00:1e:33:25:9f:46
       taille: 1Gbit/s
       capacité: 1Gbit/s
       bits: 64 bits
       horloge: 33MHz
       fonctionnalités: pm msi pciexpress msix vpd bus_master cap_list rom ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation
       configuration: autonegotiation=on broadcast=yes driver=r8169 duplex=full ip=192.168.1.72 latency=0 link=yes multicast=yes port=MII speed=1Gbit/s
       ressources: irq:18 portE/S:1000(taille=256) mémoire:a2500000-a2500fff mémoire:a1400000-a140ffff mémoire:a2520000-a253ffff

lsmod | sort
acer_wmi               24576  0
ahci                   36864  1
autofs4                45056  2
cfg80211              622592  3 iwlwifi,mac80211,iwldvm
coretemp               20480  0
drm                   393216  11 i915,drm_kms_helper
drm_kms_helper        163840  1 i915
fb_sys_fops            16384  1 drm_kms_helper
i2c_algo_bit           16384  1 i915
i915                 1568768  9
input_leds             16384  0
ip_tables              24576  0
iwldvm                208896  0
iwlwifi               299008  1 iwldvm
joydev                 24576  0
ledtrig_audio          16384  2 snd_hda_codec_generic,snd_hda_codec_realtek
libahci                32768  1 ahci
libarc4                16384  1 mac80211
lp                     20480  0
lpc_ich                24576  0
mac80211              745472  1 iwldvm
mac_hid                16384  0
mc                     45056  4 uvcvideo,videobuf2_common,videodev,videobuf2_v4l2
Module                  Size  Used by
parport                49152  3 lp,parport_pc,ppdev
parport_pc             32768  0
ppdev                  24576  0
psmouse               139264  0
r8169                  77824  0
realtek                20480  1
sch_fq_codel           20480  2
serio_raw              20480  0
snd                    69632  16 snd_hda_intel,snd_hwdep,snd_seq,snd_hda_codec,snd_timer,snd_rawmidi,snd_hda_codec_generic,snd_seq_device,snd_hda_codec_realtek,snd_pcm
snd_hda_codec         118784  3 snd_hda_intel,snd_hda_codec_generic,snd_hda_codec_realtek
snd_hda_codec_generic    73728  1 snd_hda_codec_realtek
snd_hda_codec_realtek   114688  1
snd_hda_core           77824  4 snd_hda_intel,snd_hda_codec,snd_hda_codec_generic,snd_hda_codec_realtek
snd_hda_intel          36864  3
snd_hwdep              16384  1 snd_hda_codec
snd_intel_dspcfg       24576  1 snd_hda_intel
snd_pcm                94208  3 snd_hda_intel,snd_hda_codec,snd_hda_core
snd_rawmidi            32768  1 snd_seq_midi
snd_seq                61440  2 snd_seq_midi_event,snd_seq_midi
snd_seq_device         16384  3 snd_seq,snd_rawmidi,snd_seq_midi
snd_seq_midi           20480  0
snd_seq_midi_event     16384  1 snd_seq_midi
snd_timer              32768  2 snd_seq,snd_pcm
soundcore              16384  1 snd
sparse_keymap          16384  1 acer_wmi
syscopyarea            16384  1 drm_kms_helper
sysfillrect            16384  1 drm_kms_helper
sysimgblt              16384  1 drm_kms_helper
uvcvideo               90112  0
video                  49152  2 acer_wmi,i915
videobuf2_common       45056  2 uvcvideo,videobuf2_v4l2
videobuf2_memops       20480  1 videobuf2_vmalloc
videobuf2_v4l2         24576  1 uvcvideo
videobuf2_vmalloc      20480  1 uvcvideo
videodev              184320  3 uvcvideo,videobuf2_common,videobuf2_v4l2
wmi                    28672  1 acer_wmi
x_tables               32768  1 ip_tables

iwconfig
enp2s0    no wireless extensions.

wlp1s0    IEEE 802.11  ESSID:off/any  
          Mode:Managed  Access Point: Not-Associated   Tx-Power=0 dBm   
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Power Management:off
          
lo        no wireless extensions.

ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: enp2s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 00:1e:33:25:9f:46 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.72/24 brd 192.168.1.255 scope global dynamic noprefixroute enp2s0
       valid_lft 84167sec preferred_lft 84167sec
    inet6 fe80::f28c:a706:6aab:3700/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever
3: wlp1s0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether 00:26:c7:57:54:8e brd ff:ff:ff:ff:ff:ff

sudo iwlist scan
enp2s0    Interface doesn't support scanning.

wlp1s0    Interface doesn't support scanning : Network is down

lo        Interface doesn't support scanning.
uname -r -m
5.4.0-62-generic i686

cat /etc/network/interfaces
# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback

nm-tool

La commande « nm-tool » n'a pas été trouvée, voulez-vous dire :

  commande « dm-tool » du deb lightdm

Essayez : sudo apt install <nom du deb>

sudo rfkill list
0: acer-wireless: Wireless LAN
	Soft blocked: no
	Hard blocked: no
1: phy0: Wireless LAN
	Soft blocked: no
	Hard blocked: no

nmcli connection show
NAME                 UUID                                  TYPE      DEVICE 
Connexion filaire 1  9d11ea12-c8b2-323f-b9ae-97992140b144  ethernet  enp2s0

Voilà! merci d'avance pour votre aide
Bonjour,

Voir la documentation : [doc]acer_wmi[/doc] permettant de blacklister le module avec la commande :
echo blacklist acer-wmi | sudo tee -a /etc/modprobe.d/blacklist-acer-wmi.conf
Suivi d'un redémarrage du système.

(§ 6 B > [Tuto] Pas de Wi-fi ? Eléments importants à vérifier)
Merci pou ta réponse Xubu.
j'ai tapé la commande, le problème est toujours présent
Montre : 
rfkill list all
iwconfig
nmcli dev wifi
Xubu 1957, j'ai utilisé la commande que tu donne dans le post intitulé "Pas de Wifi? Elements importants à vérifier". Voilà ce que ça donne 
nmcli dev wifi
IN-USE  SSID  MODE  CHAN  RATE  SIGNAL  BARS  SECURITY
Je n'ai pas de 2ème ligne ayant comme entête "Livebox"
Normal?
Je voulais voir aussi, puisque tu as exécuté la commande donnée au #2 : 
rfkill list all
J'ai aussi utilisé les commandes suivantes, dont le résultat est, me semble-t-il non conforme 
<pre>sudo iw dev wlp1s0 scan
command failed: Network is down (-100)
</pre>
sudo iw dev wlp1s0 link
Not connected.
Essaye : 
sudo ip link set wlp1s0 up
rfkill list all
0: phy0: Wireless LAN
	Soft blocked: no
	Hard blocked: no
1: acer-wireless: Wireless LAN
	Soft blocked: no
	Hard blocked: no
iwconfig: déjà posté, voir ci-dessus
Tu avais passé : 
echo blacklist acer-wmi | sudo tee -a /etc/modprobe.d/blacklist-acer-wmi.conf
et redémarré l'ordi ?
oui l'ordi a bien été redémarré
et pour la dernière commande demandée: 
 sudo ip link set wlp1s0 up
RTNETLINK answers: Input/output error
Tente : 
sudo modprobe iwlwifi
sudo mdprobe iwlwifi s'exécute mais ne retourne rien
Xubuntu a été installé via clé USB bootable. Mais j'ai fait une installation directe, sans passer par l'étape d'essaie
Si tu as la clé bootable, il faut tester, pour écarter une panne matérielle de la carte wifi.
je ne comprends pas. Xubuntu a été installé, l'ancien ssyt d'exploitation effacé, je ne peux faire une session Live, il me semble, non?
extrait du § 2 de la Doc a écrit Cette option est fort utile pour tester Ubuntu et son bon fonctionnement avec votre matériel (affichage, son,…) sans rien changer dans votre ordinateur.
OK, mais bon l'ancien syst d'exploitation étant supprimé, que reste t-il comme option?
C'est simplement pour tester le wifi.

Tu as regardé la Doc au #14, en cliquant sur les liens ?