As stated in Wikipedia,
Stadia is built on Linux servers and Vulkan is their graphics API.
But it is not possible to consider it a Linux platform, some game will not run on it anyway
A tag to cover the games available on other platforms sounds ok, but taking for example Assassin's Creed Odyssey, it is available for Win, PS4 and XboxOne ...
Should we tag all three ? If the PS4 one is tagged "available on Stadia", it seem like the PS4 version can be played there, right ?
And who buys a Stadia game, which game is he supposed to marks as "own" in UVL ?
Any ideas ?