Ok, so I manage to unlock the menu by pressing alt, but I still don’t know what it is searching for when the menu is displayed.

More important: I found a fix for the problem, I overwrote the file /opt/retropie/emulators/retroarch/bin/retroarch by the same file I had on another SD card (with retropie 3.1), and now everything works fine again. It’s weird because retroarch hasn’t been updated between 3.1 and 3.2.1, we still have retroarch version 1.2.2, but the files size are slightly different.