I've always played with EAC turned off on a private server or just single player (I play on Linux via Proton and intend to play on the Steam Deck now too). I haven't played for a while but as of some recent update EAC brings up this loading bar even though I (think) I have it set to off, I did the last time I ran the game. The bar just fills and gets stuck. Is there a new way to load the game with EAC disabled so I can continue playing? Performance was great on linux on AMD GPUs btw so should hopefully be good on the Steam Deck too. I've also heard that EAC have added an option to enable linux via proton support and it's just something devs have to turn on, that would be awesome if possible as a lot of public servers run EAC and also running a server via linux is a much better setup so adding EAC to that would be great for dedicated servers. As for windows, I haven't booted into it for over 3 years now and have it completely removed and would probably just give up playing the game all together over going back to it.
The latest update with new EAC seems to be working in Proton now so no longer need to disable EAC and can play on linux once again as well as on the Steam Deck too.
