I finally made it, the problem was not that my printer was not recognized but that I did not "give" the usb bus to the container.
An other problem I encountered was that kodi already used the avahi port and and needed it to advertise my printer on my local network
I solved that by asking for a second IP for my device
Check your printer can be found with
Save its location in a variable, my printer is a Canon, change with yours
BUS=$(/opt/sbin/lsusb|grep Canon|awk '{print $2}')
DEV=$(/opt/sbin/lsusb|grep Canon|awk '{print $4}')
DEV="${DEV%?}"
PRINTER="/dev/bus/usb/$BUS/$DEV"
Then I finally ran the docker command
docker run -d -p 192.168.1.32:631:631 -p 192.168.1.32:5353:5353 -e ADMIN_PASSWORD=mySecretPassword --name cups-server --device=$PRINTER ydkn/cups:latest
Now, from another device on the local network try https://192.168.1.32:631, go in the administration panel and add your printer (username admin, password mySecretPassword which you have of course changed)
Now add a printer, search a printer a the network, host 192.168.1.32 and you should find it
Many thanks to Setting up a CUPS server with Docker on a Synology NAS for my Brother printer