How to get Gears 5 Multiplayer working on the Steam Deck
You can now play Gears 5 Horde mode on the Steam Deck with a very simple change
Gears 5 recently got updated to fix the launch issue on the Steam Deck, meaning you no longer need the GE-Proton version to work around the anti-cheat fix.
However, the current Standard Proton8-02 still doesn't allow access to multiplayer
Switching to Proton7.0-6 or 7-17 fixes the multiplayer error (thanks SteamDeckLife)
Which will then allow you to play Horde mode and other multiplayer modes just fine
If you previously were using the GE-Proton version that still errors going to multiplayer, you need to delete your proton files for the game from the developer menu or verify your files.
Alternatively, you can rename the folder that was backed up as part of the GE-Proton fix, you can follow all of those steps in our video at the top of the page if you get stuck.