I hope I've made it easy to see that, if you come across an Arduino or similar device whose bootloader is messed up, it isn't too arduous a task to burn a new one. As long as you have access to a Uno or similar, the IDE and some cables, you can be on the way to uploading...
Should burn the bootloader to the atmega32U4 Arduino CLI version 1.0.2 Operating system Windows Operating system version Latest updates Additional context INFO[0007] Executing arduino-cli burn-bootloader ERRO[0008] Killing discovery process: TerminateProcess: Access is denied. discovery=rp2040 ERRO[0008...
The whole source is 1.4G, of which you’ll only need 16M, so you may just want to use the sources installed by the IDE. On Ubuntu, see /usr/share/arduino. I recommend making a copy as you’ll need to make some changes. Change to the ./hardware/arduino/bootloaders/optiboot directory...