“Steam Deck does not support BattlEye for GTA Online,” thechangelogbaldly notes.
“You will be able to play GTAV Story Mode but unable to play GTA Online.”
Apparently, it’s as straightforward as sending BattlEye’s vendors a mail.

In their changelog, Rockstar lay the responsibility for the loss of compatibility at Valve’s door.
This, players have been doing.
If there’s one thing everybody can agree on, it’s that GTA Online has a cheating problem.
I’m interested to see how they’lltackle that and GTA Online in generalafter the release ofGTA 6.