(With a Linux version or at least works good with Proton) Edit: just bought disco Elysium, going to post updates in the comments when I try it tomorrow. It’s on sale until tomorrow in case anyone is going to purchase it.
Pretty sure Portal and Portal 2 are playable in Linux.
They are more than just playable. They have native versions, because Valve wants to push gaming on Linux. Both are awesome games! I have already played them.
I also think the smartest thing Valve ever did was add Proton to their Linux platform. They are going to capture about 90% of gamers migrating from Windows to Linux. It’s a lot easier for gamers to use a pre-configured platform than fiddle with Wine settings for each game.