Recently stumbled over a game that did that a bit differently. On the steam page there is only support for Windows listed. But it actually downloads a Linux version. That version worked just fine for me, but they say they can't support it, that's why it's not listed. So there is more than single "supported" boolean (and games can list required Linux version in the requirements section I think).

https://steamcommunity.com/app/378720/discussions/0/49012573... is their explanation, https://store.steampowered.com/app/378720/Thea_The_Awakening... the store page. Great game btw.