There's been a few efforts to get Half-Life: Alyx playable without VR and the latest is HLA-NoVR, out now and it's now possible to play it through, even on Steam Deck too.
ProtonUp-Qt gives you a hassle-free way to install various compatibility tools like GE-Proton, Wine-GE, Luxtorpeda and others for Steam, Lutris and the Heroic Games Launcher.
Open Hexagon is very much Super Hexagon hyped up to max, open source and just absolutely nuts to play. A fresh upgrade is out now and it sounds great, especially for Linux desktop and Steam Deck players.
ROCKFISH Games have now launched EVERSPACE 2 and it looks awesome! One of their original Kickstarter promises did not make it though, with Native Linux support being cancelled as they will support it with Proton instead.
It's official, Valve put The Last of Us Part 1 through Deck Verified and gave it an Unsupported status on Steam Deck. Not really a good look for either Valve or Naughty Dog.
Have a PC hooked up to your TV or need a Linux distribution that might work better on a handheld PC? A new release of ChimeraOS is here, and it's a necessary upgrade. Think of it a bit like SteamOS with fancy extras.
Ah yes, launchers and external online services, what a nuisance they can be for Steam Deck and Linux desktop players. Thankfully, Valve keep working away on Proton to fix up issues.
Here's an interesting data point for you, The Pale Beyond a polar exploration game set in an unforgiving frozen wasteland managed to do well on the Steam Deck.
Steam Deck and Steam desktop both got a fresh Beta release, with plenty of bug fixing involved and Valve are dropping support for older versions of Windows.
Revhead, a racing sim all about actually building your own vehicle, recently had an upgrade with the developer now supporting the Steam Deck. It also has Native Linux support.