I found it impossible to set up 11 pro without a Microsoft account. Did you put one in for install and disable it after?
On 10 if you cut network access during install it’d let you set up offline accounts. On 11 it refuses to finish the installation until you connect to the internet somehow. I had to put my linux laptop in AP mode and connect a patch cable to the windows PC because i hadnt loaded the wifi drivers on the USB i had.
This is not my experience at all. I was recently trying to play Command and Conquer: Tiberian Firestorm, an older RTS on Windows. I own the game through Steam. On Windows, the game wont open. It crashes immediately on launch. If i run the game in XP compatibility mode, it launches but when playing the game there is some sort of microstutter: every unit is blinking, the mouse cursor is blinking, and the game plays at a crawling pace. Also everything freezes whenever you move the camera.
When i boot into Fedora on the same PC, install with steam and launch with Proton, the game works fine. I was even able to install a resolution patch for windows to get higher resolutions available.
I find this to be a pretty common experience for me when trying to play older Windows PC games. There are quite a few I cant seem to get working (or playable) on Windows, but that work fine on Linux. I mostly play older games anyway so for me, Linux is more of a game console OS.
Sorry to hear Battlenet doesn’t work for you. D4 is another one i play only on Linux, in thas case because i get some weird graphical artefacts when playing on Windows. I haven’t bought the new expansion yet though, maybe after the holidays are over.