Steam – Consistent disconnection by VAC in Linux, despite verifying local file integrity

I got disconnected from an official Team Fortress 2 server by VAC using my Linux machine, even though I have not changed the game files in anyway nor have I added any modifications. Yet, after verifying the integrity of the game files twice, I'm still being disconnected. Rebooting the machine doesn't seem to help either.

I don't have my firewall activated, I use GUFW; this just happened spontaneously.

What is causing the issue and how should I fix it? If all else fails, I might as well reinstall the game.