DCS World and MSFS2020 play on Linux just fine. MSFS2020 is flawless; DCS World has a few visual glitches with smoke tessellation and MFD textures that need to be converted before working, but besides that it's great. I fly modded and first-party modules on multiple maps, hours at a time, zero complaints.

That’s interesting… have you tried MSFS2024? That’s my main driver for now; god it would be amazing if I could run it on Linux. I’ll definitely need to try DCS on Arch! By the way - what module would you recommend (apart from F-18)?

Haven't tried MSFS2024, but ProtonDB suggests that it works okay. The 2020 version is definitely set-and-forget once you log into your Microsoft account.

Module-wise - once you have the F/A-18, a lot of the other modules feel like wasted money. I can wholeheartedly recommend the AJS37 Viggen when it's on sale, for $30 it's got a lot of flexibility and surprisingly simple systems for a 1970s jet. It's very easy to memorize the cold start process in the Viggen too, which makes it a joy to get off the tarmac. The JF-17 is also a barrel of fun, and much easier to fly/fight in than the F-16 if you don't have a HOTAS and don't need JHMCS. Besides that, the only other modules I can fully recommend is the Syria map, Persian Gulf map, and Flaming Cliffs for all the modded planes it unlocks. Not personally a fan of the Sinai map right now, and the Apache is very difficult to fly without a copilot/gunner in the second seat. Black Shark 3 is fun, but one of the most goddamn complex modules in the game. Even with translated cockpit labels, you'll be permanently conjoined to a YouTube guide telling you how to do the most basic flight maneuvers.