The runtime is for launching games, not Steam itself. You can check the runtime selection in Compatibility tab of Steam and of each game. If your Steam Flatpak install doesn’t work, the issue is likely somewhere else.

I’d suggest trying to launch the flatpak from the terminal and seeing if there’s any strange logging.

Probably a trans woman? From the name and Fed instance.

Doesn’t the poster look underage as well?

US cheap? 10 bucks a beer cheap? I get five beers and five meals for that price in some areas of Europe.