Hi! I got a Steam Deck for myself as a late Christmas present, but was disappointed to see that both DayZ & Arma 3 are hobbled because the launchers on Steam OS don't handle Mods correctly.
You can use the launch parameter -noLauncher to bypass and get straight to the game, but PC DayZ & Arma really are about the mods.
With the quality and price of the Steam Deck, this could become a significant community for BI if they can solve these issues.

1. Fix the launchers so Steam Workshop Mods work on Steam OS.
2. Give us the ability to disable the downloading of certain subscribed mods of our choice so we don't fill the storage of our Steam Decks.

ps, If you haven't given DayZ or Arma 3 a go on the Steam Deck, you should, it looks and runs great!
Thanks, Rob.