"EAC supports Linux, but devs just won't turn it on" is the clickbait answer, but the details are more nuanced. EAC has multiple security levels that a title can set based on the threat model of the game, and most games with heavy MTX that use EAC shy away from it, largely because Fortnite doesn't do it. EAC is owned by Epic, and if Tim Sweeney says that you can't do MTX on Linux safely, then any AAA live services game with in-game MTX is going to shy away from it, regardless of how true the statement actually is.

You are only safe if you run Tim's rootkit :)

The Finals has mtx, is protected by EAC, and is playable on Steam Deck.

Throne and Liberty, which is also protected by EAC and has mtx, is also playable on Steam Deck.

So this is bullshit and it clearly shows it's the publisher's choice. What Sweeney thinks has nothing to do with it.

"MTX" as in, microtransactions?

What do microtransactions have to do with anticheat?