I've got a problem and I really hope it's just a small step for you, but a big leap for mankind, or at least for me.
I have a Rasberry3 working very fine on a SDCard. I bought a new Raspberry4, of course without reading about the "dont put your Raspb3 SD-Card into the 4"-part.
So I dit. It didn't start. Of course.
Putting back the card into the Rasp3. Didn't restart either.
So here's the question:
What did the Rasp4 do to the SD card, while it was trying to boot. Did it change boot settings or other data, like owner settings of certain files? I need to get that card on the Rasp3 rerunning, and I dont have a monitor or keyboard for it, so see whats going on while booting. Only the filesystem and a linux terminal to write on that SD. So I really hope that somebody knows what the bootloader did on the filesystem, while he was trying to boot on the raspberry4.
thank you :)