I want to install an OS once, and never be forced to change it on that machine.

I’d be wary of putting all your eggs in a single basket, many people believed Windows was the be-all OS until Microsoft started making funky decisions ultimately changing people’s perspective of their business.

Steam is great now but consider who is going to replace Gabe Newell when he retires or passes away.

I prefer Valve. 800lb gorilla, main driver of Proton, not likely to suddenly vanish or change leadership, brand recognition means many people will develop extensive documentation and implementation specifically for SteamOS

Under the hood SteamOS/Bazzite are Arch based whereas Ubuntu/PopOS/Linux-Mint are Debian based, the documentation that really matters is going to come from these primary derivatives of these distributions.