That would be the easiest path, but would cost you!
You can try to install the battle.net version via Lutris:https://lutris.net/games/diablo-iv/ and it should work. I haven’t tried this game in particular, but had a great experience with Lutris in the past.
It is a great front end for Wine/proton and a database of install scripts and configurations for many games.
Bit off-topic, but if you would want to also play games from the Epic store or GOG, be sure to try Heroic Launcher.
Do I have to re-buy it for Steam then?
That would be the easiest path, but would cost you!
You can try to install the battle.net version via Lutris: https://lutris.net/games/diablo-iv/ and it should work. I haven’t tried this game in particular, but had a great experience with Lutris in the past.
It is a great front end for Wine/proton and a database of install scripts and configurations for many games.
Bit off-topic, but if you would want to also play games from the Epic store or GOG, be sure to try Heroic Launcher.