Hi @florent5 welcome to the /e/ forum.
The pie to Android 10 (Q) turned out to be the blocker. So you should really be looking at a new install. Users sometimes seem to worry about lock and unlock stage, but it is really quite black and white.
You will have to Format data, so you need to prepared for that.
Firstly is your phone locked ?
Can you find your way to your device pages by searching from https://doc.e.foundation/devices ?
Can you boot your phone into bootloader (just to explore) and then boot to system to get out of bootloader ?
The bootloader view includes the “locked status”.
Are you using the cloud successfully ? Anything you see there from your PC will be synced back to your phone after your clean install
Prepare anything else you need to backup. Search for recent backup threads on the forum.
Here is a useful tutorial [HOW-TO] Flash /e/-OS on Fairphone 3 using Debian based GNU/Linux