Thanks for the answers. Yes the cable OK is fine it’s the one from the pixel box, I used it to flash e OS before.
I did’nt try using GIT Bash for the fastboot prompts (not used to the “gramar” of git bash").
Here are the photos:
Sorry it’s in french.
Do you have a fastbboot drivers problem ? [Solved] Windows does not see my phone in Fastboot mode
With the phone in fastboot mode (using power + volume down), I can’t see the phone neither in the Device manager window. So I can’t fix possible driver issue
You can only change this while a data cable is connected between device and PC
Yes usually it works changing it when connected but here no, the options are in grey.
EDIT:
I had to reset USB-debugging authorizations and it worked smooth after that. Thanks for the help!