Well, thank you for your response. I “succesfully” had the “no command” screen, then I had some troubles entering in recovery mode. Finally, this did the trick : (from another topic)
Being on the “no command” screen and then holding down the power button for 3-5 seconds and then press and release the Volume up button worked for me
Data wipe, then reboot.
After 2 min of blue dots spinning, my FP3 finally booted!
Thank you so much! 