I mean, Steam has it flagged as having Linux-native support. Normally, on a Linux system, if there's a Linux-native binary, Steam will use that, not the Windows version.

...oh, wait. I did assume that you were running it via Steam, and you didn't actually specify. Are you starting it from something else? Like, did you get it from GOG? Epic Games? Someone other than Steam?

EDIT: Ah, EGS is Epic Games. Okay, I've never used their store, have no idea how they set this up. Let me try taking a look.

EDIT2: Based on their store page for the game, they only provide Mac and Windows binaries, so, yeah, it's probably running a Windows binary.

EDIT3: Okay, I'm assuming that this:

https://heroicgameslauncher.com/_next/static/images/heroic_install-eb9d446009e809a8d91cfa31213e27d4.webp

Is showing the default install path for games that Heroic installs, which looks like it's under ~/Games/Heroic. Sorry, you did mention that in your post, couldn't figure out what you were talking about. So if this uses the same convention that Steam does, then it's probably gonna be that the WINE prefix is the "pfx" directory in there.

https://old.reddit.com/r/SteamDeck/comments/v58ju3/how_to_find_my_local_saves_made_through_heroic/

Turned out with the default prefix heroic was saving my games in /home/deck/Games/Heroic/Prefixes/The Witcher 3 Wild Hunt/pfx/drive_c/users/steamuser/Documents/The Witcher 3/gamesaves/

So the "pfx" will be the WINE prefix.

On Windows:

https://steamcommunity.com/app/640820/discussions/0/4029096934194613470/

The default folder for Windows is C:\Users\[username]\AppData\LocalLow\Owlcat Games\Pathfinder\Kingmaker\Portraits.

So it'll be:

~/Games/Heroic/Prefixes/<gamename>/pfx/drive_c/Users/<username>/AppData/LocalLow/Owlcat Games/Pathfinder/Kingmaker/Portraits

I don't know for sure what the "gamename" is, but there should be a pre-existing directory there. I also don't know what your is in that path, and it depends upon how Epic configures WINE

at my above link, it's "steamuser", but that's using the Epic Games launcher on a Deck, and I suspect that they may always use "steamuser" there. Again, should be a pre-existing directory there, probably be your username on the Linux system.

Sorry for the confusion there, just hadn't used Epic Games' launcher myself, didn't understand that you were specifying that you were using it.