I have a 3770k system my son is still using. It is going strong.
I dread the day I can't update it any more. This will force many people over to other systems.
I can swap out the motherboard, CPU, and memory. But what e waste.
I'll also have to reformat my other sons 3900x as secure boot isn't on. That's an Uber pain in the tail.
With those systems, you are on Windows 10 (or Linux) forever. If you want to keep them forever.
That said: with my motherboard (currently not working, but not because of Windows), I enabled secure boot several years ago. Does not require reformat. Worked seamlessly by itself, but Bitlocker with it got a little cranky under certain circumstances, demanding an unlock code that's only available by logging in to my MS Account on another computer or my phone, then laboriously typing it in.
Even the GPT (vs MBR) disk format change can be done by a tool included with Win10, without reformatting.
In my case, the motherboard and CPU were new enough that Win11 upgrade went off without a hitch. No worse than a feature update in Win10. Yes, I'm unhappy with the taskbar and several other time- and keystroke/click-wasting UI choices MS made, but otherwise I've had no software or driver compatibility issues that weren't already present in Win10. So if you are willing and able to update your hardware, it's a reasonable (and so far free) upgrade from Win10, however you got it.
EDIT: as for open-source, I have 2 pieces of software that I use semi-regularly that are NOT open source or, at least, legitimately freeware (not stolen). All of my software that I used in Win10 also works in Win11, including some stuff (mostly games) that dates from Win98. So Win11 is for pushing people out of open source? I don't think so.