Let's say I owned a pretty retro device some years ago, but it broke beyond my repairing capabilities and I trashed it.
Would it be still on-topic to ask e.g. how I could have fixed a specific error (just out of curiosity) or how I could have done this and that with it?
I am aware of the problem that it's impossible to verify potential answers on no longer existing hardware, so it could be difficult to both word the question in a detailed enough way and to later accept an answer.
However, I think this could become interesting for a larger community, as our topic here is about old hard- and software. I am sure most members here do not own all of the pieces they're going to ask a question about, unless they work at a museum maybe...
So where exactly do we want to place the border?
No hypothetical questions about problems on stuff you don't have access to. Only ask about hard facts that could written into an encyclopedia.
Only questions that could likely somehow be reproduced on another device of the same model.
Like e.g. "My X Model Y always showed an error 02 when trying to boot from a foreign HDD. I don't have it any more, but (how) could I have fixed this?"
All questions about old computer stuff are on topic as long as you word the question detailed enough to be answerable.
Anything in between those options?