It's not an anti-cheat problem, it's an OpenSSL issue caused by moving to a CPU with a certain extension. I've found pointers with how to fix it online, but I didn't know how to apply the fixes on Linux. I now know I can use WineTricks. I'll write up an answer later, when I've attempted fixing it. Thanks for the answer, though; I noted in chat that the issue seems to be with OpenSSL, but I should've commented here.

Unlike Apex Legends (which uses EAC), the game still launches. There is a Linux version of EAC, though, which the Steam version of Apex Legends uses.

Wow! That's interesting and weird. I'm curious to see what exactly the OpenSSL issue was, and also how you confirmed that.

I don't really know what the anti-cheats do exactly, but they behave in unpredictable ways. For example not every game with EAC is equally strict or encounters the same problems. Maybe EAC has some way where you can customize your cheat detection or something, and developers do it in different ways. I don't think EAC etc. necessarily treat the Linux version the same as the Windows version, also.

To be honest, I try to avoid anti cheat where I can, and luckily not many competitive multiplayer games interest me. But if you really want to play a game with EAC, then it would be a problem - dunno what the solution is (besides dual booting windows for just that game).

In any case, sounds like the issue is not anti-cheat anyway. IMO troubleshooting games in wine is a useful topic for this site (or https://proposals.codidact.com/categories/67/tags/7470). But I dunno if it makes sense to basically duplicate what ProtonDB already does. For Codidact, it's probably more useful to focus on recognizing symptoms and general workarounds, rather than documenting each individual game. So I wonder if there's a way we can reframe questions like this to be more like "How to deal with symptom XYZ, which happens for example in Titanfall 2?"

But to be clear I have no objection to this question per se.

Wow! That's interesting and weird. I'm curious to see what exactly the OpenSSL issue was, and also how you confirmed that.

I'll definitely get around to fix that. I just figured I enjoyed playing my other games on the new hardware so much that I postponed fixing this one. :P

I really don't think there will be an issue with EAC in this particular game. Apex Legends doesn't get past the EAC check in Lutris/EA, but it does bundle a Linux version in Steam.

For Codidact, it's probably more useful to focus on recognizing symptoms and general workarounds, rather than documenting each individual game.

If the solution is the exact same for every game, then yes, I agree. If not, as Codidact is a Q/A site capable of hosting millions of questions and answers, I think we're a great fit for having a Q/A for each game. Of course, the more we can gather together, the better. But, until we actually have more games to list, I'd say we don't need to future-proof at this point.