Launching sometime in October, the cross-platform anime RPG Blue Protocol: Star Resonance will work on Steam Deck but probably not Desktop Linux.
As for why — because it's going to be using Anti-Cheat Expert (ACE). Other games that use this usually either work only on Steam Deck with SteamOS or don't work at all, it's one of the most problematic anti-cheat systems for playing games on Linux platforms. Wuthering Waves appears to be the outlier here, since that can work on Desktop Linux too with a tweak.
The developer responded to my email to simply note:
ACE supports the latest version of the Steam Deck system (Steam OS 3.7.8). For older versions, players are suggested to update the system to the latest version.
And the game currently doesn't support Linux or Mac.
Yes, yes, I know - Steam Deck is Linux too, but Anti-Cheat Expert (ACE) often targets the hardware directly.

Direct Link
I'm still hoping eventually this anti-cheat situation gets less annoying for Linux gamers across Desktop / Steam Deck and other SteamOS devices. Especially if the leaks about a new Steam Machine come true.
Be sure to keep an eye on our anti-cheat page for any change in the status.
ACE supports the latest version of the Steam Deck system
And if it's like the other games that use it it's likely to only work on Deck LCD but won't work on Deck OLED, as well as not working on the millions of other Linux PCs.
One to avoid, obviously.