[pqtyw]

It's hard to tell but it seems that no more than 20% of Steam users have pre 8th gen Intel CPU. I'm looking at CPUs with 4 or less cores and Intel was shipping them as late as 10th gen so it's probably considerably more so it's probably considerably less than that.

AFAIK most CPUs with > 4 cores are 8th gen or newer and should be supported (besides old Xeons, Skylake-X and such but I doubt there are that many of those ). Also not sure about AMD but their market share was quite low pre 2020.