Valve are committed to Linux and Linux gaming with Steam, that much is currently clear. They're working with so many contractors on various things, and it seems not everything is as people think.
Recently, Collabora, one of the companies they're contracting with went over a bunch of details like their upcoming Linux Kernel work coming to Linux 5.11 and then a quick overview of everything. Many people thought that a lot of the ongoing work, like the Kernel work was to help things like anti-cheat with Steam Play Proton and it was mentioned by Collabora however it seems that's not exactly the case. Valve developer Pierre-Loup Griffais commented on Reddit to clear up on some speculation, mentioning that Collabora did some speculating of their own.
Griffais mentioned the Kernel work is "nothing to do with anti-cheat" and is instead for anti-tamper and DRM to function properly while also mentioning proper anti-cheat support "is still a long ways out and will need vendor support". That alone is going to be a sore spot for a long time for multiplayer titles run through the Proton compatibility layer, which is why we have an FAQ entry for Easy Anti-Cheat and BattlEye (the most popular) on our dedicated Proton site.
Other points mentioned are that the Steam Linux Runtime Container has nothing to do with security, OpenXR for SteamVR was done by Valve directly (Collabora's own VR work like Monado is unrelated), and the "image-based updater work" is actually towards improving live USB media to update them without losing user data.