Despite the name, VRChat is not a VR-only space and it's incredibly popular. Recently though, they added in Easy Anti-Cheat and the community is currently very unhappy with it.
Why does such a social space need anti-cheat though? As they said in their announcement modified clients became a big problem. They allowed users to "attack and harass others" which caused endless moderation problems. Plus, they explained that every month "thousands" of people have their accounts stolen due to these modified clients. So it is a big issue.
The downside is that some big features that a lot of people enjoyed have been lost, since no modified clients can be run, and some people can't play at all due to it. The developer said addressing those concerns is their "highest priority" and they're moving around their roadmap for it.
Since Easy Anti-Cheat supports Linux, the developers ensured and tested it working for Proton and Steam Deck so there should be no issues continuing to run it. As they said in their blog post announcement:
Does this prevent people from playing VRChat on platforms like SteamOS on the Steam Deck? What about Linux via Proton?
No, we’ve tested this! EAC works fine on these platforms. Thanks to Valve and the Proton team for all their hard work.
Clearly they've hit a nerve with the community though, as it's now getting review-bombed on Steam with the most recent user reviews hitting Overwhelmingly Negative.