Run the memory test that comes with windows. It takes like an hour or something, and will tell you if the memory is malfunctioning - that would explain all the mysterious crashes.
I've had this problem out of nowhere one day (computer would not stop crashing randomly) and it turned out to be a defective memory stick. All good after replacing it.
Sometimes bad quality ram chips, or set with the wrong timing in UEFI, or just not properly seated ram, can cause problems similar to what you've described. Anecdotally I have W11 installed on 5 different machines and none of them have the issues you're describing.