Even though FINAL FANTASY VII REBIRTH is rated as Steam Deck Verified, it did launch with some problems on Linux / Steam Deck but Valve's Proton developers are moving quickly to improve it.
Read the full article here: https://www.gamingonlinux.com/2025/01/final-fantasy-vii-rebirth-should-work-better-on-linux-steam-deck-with-the-latest-proton-hotfix/