I‘ve played GW2 a lot and pretty much exclusively on Linux for a few years now and it‘s been pretty smooth.

For the best experience, make sure your graphics driver is up to date (as of now it should start with 550, 555 or 560).

I‘d also recommend installing the game via Steam, as this makes the whole compatibility stuff far easier. The Steam version also works if you want to log in with an Arenanet-account. Just add this launch option (note the capitalization; it has to be exact) and you‘ll be able to log in with your existing account:

-provider Portal

Just make sure not to buy anything via Steam as purchases won‘t be associated with the correct account.

You‘ll also want to make sure (although it‘s probably set as default by now) to use Proton 9.0 or above, as the game‘s launcher is really stuttery in previous versions.