Not only Steam Deck, all Linux community on desktop...​

We can upvote an already opened ticket to raise awareness of the issue:

Ticket

This is also a PC/Steam issue (win 11) for me

From Dildozer on Steam Community:

​Possible fix for windows people

The game apparently changed the way certain files can be modified causing conflicts with any mods installed regardless of they are mods that are cheating or just quality of life. If you are getting AVF connection issues and are on windows try deleting all mods and delete the space Marine 2 config file, then validate and try to launch again.

It seems that they did not either add the compatibility with proton so that Linux based distros can play the game or changed the way eac works to a point that it cannot work with Linux distros. If the latter is true then I'll personally try and get a refund due to it being a rug pull for people on Linux and steam deck, but I hope it is the former since they made it compatible with eac on launch

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