

As long as the kernel keeps supporting loading and executing processes with 32-bit code, they don’t even need to go that far. There shouldn’t be much stopping Valve from just supplying libraries themselves inside a container. In fact, that’s what the Steam Linux Runtime “Sniper” does.
Linux isn’t derived from Unix, just originally based on it. The BSDs and Darwin (Mac) would be the unfortunate casualties, but at least most of the country won’t be stuck with Windows?
Edit: And, I guess, Nintendo Switch and PlayStation 4/5. The former “borrowed” the networking stack from OpenBSD, and the latter are based on some BSD variant if I recall correctly.