It’s perfectly possible to isolate a steam install, NixOS does that by default to even get it running (on NixOS nothing is where any binary blob expects it to be). There was a very brief issue with experimental steam when they tightened up their own sandboxing and doing sandbox-in-sandbox broke stuff but that was fixed before release as Valve is, indeed, responsive, even if the distribution isn’t officially supported. But you gotta have some professionalism and have institutional continuity, they don’t want to deal with J. Random Hacker doing a one-off packaging job. Or distros trying to be smart and replace the steam runtime with their own library versions. Basically, assume that the whole thing runs directly on the kernel, make sure to have graphics drivers, and you’ll be fine running it as-is.