Ok merci des indications... Je te mets tout ci-dessous.
leo@leo-ThinkPad-X201:~$ cat /etc/sane.d/dll.conf
# dll.conf - Configuration file for the SANE dynamic backend loader
#
# Backends can also be enabled by configuration snippets under the dll.d/
# directory -- third party backends can drop their configuration file in
# this in this directory, named after the backend.
#
# The next line enables the network backend; comment it out if you don't
# need to use a remote SANE scanner over the network -- see sane-net(5)
# and saned(8) for details.
net
abaton
agfafocus
apple
artec
artec_eplus48u
as6e
avision
bh
canon
canon630u
canon_dr
#canon_pp
cardscan
coolscan
#coolscan2
coolscan3
#dc210
#dc240
#dc25
dell1600n_net
dmc
epjitsu
#epson
epson2
epsonds
escl
fujitsu
genesys
#gphoto2
gt68xx
hp
hp3500
hp3900
hp4200
hp5400
hp5590
hpljm1005
hpsj5s
hs2p
ibm
kodak
kodakaio
kvs1025
kvs20xx
kvs40xx
leo
lexmark
ma1509
magicolor
matsushita
microtek
microtek2
mustek
#mustek_pp
mustek_usb
mustek_usb2
nec
niash
#p5
pie
pieusb
pint
pixma
plustek
#plustek_pp
#pnm
qcam
ricoh
ricoh2
rts8891
s9036
sceptre
sharp
sm3600
sm3840
snapscan
sp15c
#st400
#stv680
tamarack
teco1
teco2
teco3
#test
u12
umax
umax1220u
#umax_pp
v4l
xerox_mfp
brother4
leo@leo-ThinkPad-X201:~$ dpkg -l | grep -i libusb
ii libgusb2:amd64 0.3.4-0.1 amd64 GLib wrapper around libusb1
ii libusb-0.1-4:amd64 2:0.1.12-32 amd64 userspace USB programming library
ii libusb-1.0-0:amd64 2:1.0.23-2build1 amd64 userspace USB programming library
ii libusb-1.0-0-dev:amd64 2:1.0.23-2build1 amd64 userspace USB programming library development files
ii libusb-1.0-doc 2:1.0.23-2build1 all documentation for userspace USB programming
ii libusbmuxd6:amd64 2.0.1-2 amd64 USB multiplexor daemon for iPhone and iPod Touch devices - library
ii libusbredirparser1:amd64 0.8.0-1 amd64 Parser for the usbredir protocol (runtime)
leo@leo-ThinkPad-X201:~$ ls -la /usr/*/*/* | grep -E "brother"
lrwxrwxrwx 1 root root 42 fév 5 2020 /usr/bin/X11/brsaneconfig4 -> /opt/brother/scanner/brscan4/brsaneconfig4
lrwxrwxrwx 1 root root 44 fév 8 11:18 /usr/bin/X11/brscan-skey -> /opt/brother/scanner/brscan-skey/brscan-skey
lrwxrwxrwx 1 root root 37 fév 5 2020 /usr/lib64/sane/libsane-brother4.so -> /usr/lib64/sane/libsane-brother4.so.1
lrwxrwxrwx 1 root root 41 fév 5 2020 /usr/lib64/sane/libsane-brother4.so.1 -> /usr/lib64/sane/libsane-brother4.so.1.0.7
-rwxr-xr-x 1 root root 198904 fév 5 2020 /usr/lib64/sane/libsane-brother4.so.1.0.7
lrwxrwxrwx 1 root root 41 fév 3 11:48 /usr/lib/sane/libsane-brother4.so -> /usr/lib64/sane/libsane-brother4.so.1.0.7
lrwxrwxrwx 1 root root 41 fév 3 11:48 /usr/lib/sane/libsane-brother4.so.1 -> /usr/lib64/sane/libsane-brother4.so.1.0.7
lrwxrwxrwx 1 root root 41 fév 3 11:48 /usr/lib/sane/libsane-brother4.so.1.0.7 -> /usr/lib64/sane/libsane-brother4.so.1.0.7
lrwxrwxrwx 1 root root 74 fév 8 11:17 brother_lpdwrapper_mfcj6930dw -> /opt/brother/Printers/mfcj6930dw/cupswrapper/brother_lpdwrapper_mfcj6930dw
lrwxrwxrwx 1 root root 21 fév 8 11:18 libsane-brother4.so -> libsane-brother4.so.1
lrwxrwxrwx 1 root root 25 fév 8 11:18 libsane-brother4.so.1 -> libsane-brother4.so.1.0.7
lrwxrwxrwx 1 root root 41 fév 3 11:48 libsane-brother4.so.1.0.7 -> /usr/lib64/sane/libsane-brother4.so.1.0.7
-rw-r--r-- 1 root root 41966 fév 8 11:17 brother_mfcj6930dw_printer_en.ppd
leo@leo-ThinkPad-X201:~$ ls -la /etc/udev/rules.d/ | grep -E "brother"
-rwxr-xr-x 1 root root 602 fév 8 11:18 60-brother-brscan4-libsane-type1.rules
-rw-r--r-- 1 root root 759 fév 3 11:54 60-brother-libsane-type1-inst.rules
leo@leo-ThinkPad-X201:~$ cat /etc/udev/rules.d/60-brother-brscan4-libsane-type1.rules
#
# udev rules
#
ACTION!="add", GOTO="brother_mfp_end"
SUBSYSTEM=="usb", GOTO="brother_mfp_udev_1"
SUBSYSTEM!="usb_device", GOTO="brother_mfp_end"
LABEL="brother_mfp_udev_1"
SYSFS{idVendor}=="04f9", GOTO="brother_mfp_udev_2"
ATTRS{idVendor}=="04f9", GOTO="brother_mfp_udev_2"
GOTO="brother_mfp_end"
LABEL="brother_mfp_udev_2"
ATTRS{bInterfaceClass}!="0ff", GOTO="brother_mfp_end"
ATTRS{bInterfaceSubClass}!="0ff", GOTO="brother_mfp_end"
ATTRS{bInterfaceProtocol}!="0ff", GOTO="brother_mfp_end"
#MODE="0666"
#GROUP="scanner"
ENV{libsane_matched}="yes"
#SYMLINK+="scanner-%k"
LABEL="brother_mfp_end"
