This sub seems to be pretty new to gaming and tech in general. Thats the only way to explain this kind of stupidity.
Stadia is a platform in the way that Xbox Live is a platform. It is NOT a fully custom SoC like a console has. It is a PC blade with damn near off the shelf chips with slight tweaks. A very common thing in server stacks.
Stadia servers are linux based PCs. Period. End of story. Games that are not natively on Linux yet will take a slight bit of extra work to have run optimally on these servers, but thats it.
Its the identical situation to someone playing on a Linux PC. You play with other PC players in multiplayer.