Free Windows 10 support ended for most people this past month, and the trend line of Linux usage has been quite clear leading up to this, as people prepared for the inevitable. An increase in Linux usage is also correlated to a drop in Chinese players, which did happen this month a little bit, but Linux usage is also trending up when filtering for English only. It's worth noting that for all the official support Macs ever saw in gaming, they never represented anything better than about 5% of the market.
I wish there was a graphic that showed English users with SteamOS separated from non-SteamOS users, because I think if we get 5% of non-SteamOS users, we should start to see devs pay a lot more attention. We're starting to see devs make SteamOS-specific versions (e.g. THPS 1&2 offline mode), so the next step is getting Linux-specific adjustments for more games.