There's a few other customization items that are locked away as well. I can't recall what they are, and I finally registered by copy after years of running windows 10 and 11 unregistered so I can't even look for it. It might have had to do with graphics settings (flip presentation model?), or HDR. I think there were ways to force those options with registry edits, but that's more trouble than buying a cheap $10 windows key, which is what I finally ended up doing.
I also see lots of reports that updates other than critical/security ones may not be downloaded and applied for unregistered installs, but I'm not sure how true that is (or if it's mostly moot because I know you still get the big spring/fall patches, or at least have historically).