So, this has been a standard phase of the Windows product lifecycle for 20+ years now. It doesn't really answer the problem with Windows 10 retirement and unsupported hardware on 11+ but it shouldn't be a shock to anyone.
Well, not supporting certain high end cpu's for Windows 11 is a problem. They are forcing me to either switch cpu, AND mb or not get Windows 11. The last one is fine with me, but now they stop support for Windows 10... That kinda rubs me the wrong way.
You're welcome to try Linux, it's free, easy to use, easy and free to update, and stable. I use Ubuntu because I prefer something I don't have to mess around with too much.
OneNote web interface can work as an intermediate step while you work out alternatives. May I suggest either obsidian or logseq with syncthing or webdav.
As the other reply said, I'd definitely give Linux a try. Even the gaming situation has gotten a lot better though it's still not perfect.
The CPU thing with 11 is kinda dumb but I do see why they did it. They wanted users running all the virtualization-based security features that were optional in 10. Some of those depend on a feature to minimize the amount of times the virtualized parts of the OS needs to swap to the hypervisor and back when it needs to change between user and kernel mode memory pages. All the Intel CPUs supported and all but the earliest AMD CPUs supported have a hardware feature called MBEC/GMET that speeds this up drastically. Unsupported CPUs (and AMD Zen+ which are supported) have to fall back to an emulated version of this feature but the performance penalties are high. When I was running an AMD Zen+ architecture CPU the difference in game performance between virtualization-based security being enabled/disabled was often in the range of 15-20%. It's likely the earlier CPUs from Intel and AMD suffered from far worse impacts. If I had to guess Microsoft opted for the bad press from incompatible CPUs instead of being inundated with news about Windows 11 being dogshit slow.