Humm, I installed Windows 11 on a really old Dell laptop (clean install). I'm sure it was not HW supported but it installed fine. I may have had to click something like, " Yeah I know it doesn't meet the specs"; but otherwise fine.
No, I don't like Windows but it's what my partner needed at the time.
As long as it is 8th gen Intel or newer it is officially supported. It depends on what you mean by "really old." I have hardware from the early 2000s that runs Debian.