I had pre-ordered prior to release and got it last July. The 256gb model but I’ve upgraded to a 1TB since then. I’ve had issues in the past with Heroic and debated simply running the game through Windows or installing GOG through Lutris but luckily Heroic worked.
Have you considered trying to just install GOG through Lutris? I run Diablo IV like that (via Battle.net of course) and it’s simple enough.