All games (theoretically) run on Linux -- cloud gaming is a thing. Even if you may say "B-but muh input lag" its extremely doable and reliable as of now.
This. My current connection is the most speed I've ever had and the most you can get in my area without spending a ton on business class, but cloud gaming is atrocious at best. I'm not gonna move to the city so I can get gigabit for a half decent price while spending 4 or 5 times more on housing.
Germany has terrible internet service, so no, not everywhere.
Also you would still need a cloud gaming provider that has servers close enough to your location that lag doesnt become an issue and actually offers that service in your country, which I'm not sure would be the case for all places
The only place I've seen it viable was in a speed test in Los Angeles on Verizon mmwave that achieved 6ms latency on input.
That's in addition to the controller, bluetooth, and device input lag. This 6ms is experienced both in the video feedback and in the button presses.
In certain games this lag can hamper the experience. I know with 12-16ms ping I still hit cars and walls I shouldn't have in driving games which I figured would be the easiest to stream.
Maybe fiber could achieve a less perceptible latency, but I can't imagine that rolling out faster than some people will be able to render it natively on a low end device.
Do we know the data centers are rendering the games on Linux? It's entirely possible they spin up ephemeral stripped down windows vms to host the sessions.