I recently wrote about how it's looking pretty unlikely that Rust will actually be supported on Steam Deck / Linux with Proton, and it's not looking any better right now.
Previously it was just comments from Facepunch Studios' Garry Newman on Twitter, with Newman trying to explain their thoughts on why it hasn't happened yet. Now, we have another and perhaps a bit more public / official answer with their latest official news post on the Rust website including a note at the bottom about it from Alistair McFarlane, the Producer at Facepunch, that reads:
You know, we switched to EAC's new platform with the intention of providing support for the Steam Deck, and so far we haven't done that. So when is it coming?
Well, short answer is we don't know. We don't know if it is. When we discontinued linux support in 2019, one of the core reasons was how the cheating community was exploiting the Linux platform. That's not to say that cheating was super widespread on Linux, but it was safer for cheat developers. And that's not good in a game like Rust where a cheater can ruin weeks of hard work.
Enabling proton support would mean we're asking the EAC team to provide support for a whole other platform, which we fear would reduce their ability to support Windows - our main platform. We don't know whether we should enable one platform at the disadvantage of another.
The one thing we don't want to do is to enable Proton support to only discontinue it six months later. We don't want to encourage players to spend their money on a Deck to play Rust and then be in a position where we want to take that ability away.
For now, we're still weighing up the risks and will continue to explore options with EAC. Don't expect to see Proton support in the near future, but we hope to have it enabled someday.
So it's basically the same story as what Newman explained. They don't wish to potentially open up Rust to more cheat developers again, where they don't seem to feel confident that EAC would be able to keep up with it on top of preventing the cheats on Windows too (which is obviously the main platform).
It is a genuine shame, since Rust is (while quite brutal) a great survival game and very popular. It's also interesting, because clearly they think that EAC don't provide all that great protection on Linux if they're that worried about what would happen again. While again, other games like Apex have it, they're very different games.