Browser vendors can't clean up User-Agent because the websites sniff it and break if it's "wrong" (for any random value of wrong). I'm sure there's a Bugzilla

Browser vendors can't clean up User-Agent because the websites sniff it and break if it's "wrong" (for any random value of wrong). I'm sure there's a Bugzilla bug about the "X11; Linux x86_64" in the headers, and I'd be terrified to open it.