Help Me understand Steam Deck vs SteamOS compatibility
From my understanding Steam Decks come with SteamOS preinstalled on them. Yet when you look at the list of games on steam that are compatible with Linux + SteamOS, its a small fraction.
It shows your games that are compatible with the Steam Deck which has a Linux based OS. And almost my entire library is compatible with the Deck. Can someone help me understand how this is possible? If games are compatible with the Steam Deck, why wouldn't they also work on Ubuntu for example?
"Linux + SteamOS" compatibility is a bit legacy. It mostly refers to games that have a native linux client (I believe some of the early Proton Validated games are included as well.
The Steamdeck (and generally speaking, any linux system) uses Proton as a compatibility layer with windows, and the "Steamdeck Verified" system is more relevant today. That said, even the Steamdeck verified system isn't perfect. There are a number of titles that, while verified, have some problems with the deck, typically later in the game or after running for some number of hours. There's also a vast number of games that while not "Steamdeck Verified" work perfectly on the deck and linux via proton (though you do have to enable it in the settings).
Games that have native Linux versions are uncommon, but Steam on Linux includes a program called Proton, which provides a Windows-compatible environment so that games made for Windows can run without being manually ported. It isn't exactly the same, so some games don't work quite right, which is why not every game is compatible with Steam on Linux.
Any game that's compatible with the Steam Deck should run fine on any other Linux system, as long as the underlying hardware is powerful enough.
Games that work are generally exactly the same. If you sit down in front of a Pc already running the game you cant tell the difference.
Sometimes you need to fiddle a bit to get a game working. Sometimes you click play and you play. Some developers dont want you to play their games so they dont work (anti cheat).
Most things work very well. Some games are more fun to get working than playing the game in my experience.
If the game is reasonably well-coded, there's not going to be any obvious difference between a game running on Windows, a game running native on Linux, and a game running using Proton.
I mean yeah, you could have some performance impact (usually light, occasionaly not so), maybe video not playing (some games use video formats for cutscenes which can't be distributed on Linux installs), or maybe issues with windowing (Tropico 6 has an weird bug where the game mouse pointer has a bit of offset compared to the real one, until you change screen size).
But in most cases, if it works, it works the same.