Go to desktop mode (in the power menu). Download for windows. Add to steam (still in desktop mode). Return to game mode. Bring up the settings for the game. Put game in compatibility mode. Game will now work. I've done this multiple times with multiple games.
Were it that easy, I'd have done that. Perhaps I was unclear, if so I apologize. But the Rant wasn't about playing on the Steam Deck, as it was about Valve's (German) policy of outright censorship on these types of Games.
I don't know if this Game could be made available on GoG, or not, but unlike Steam at least those kinds of Games are neither hidden behind seven proxies, or just got simply flagged as being unavailable in my region.
As such that's was where I was coming from. As a noobish Deck luser I've become most adept at using non-steam Games via the Desktop Mode. Again given the commercial aspect of the product, and the fact that I'm not allowed (by my host countries insistence) to obtain it legally via the prescribed channel. Yeah that's my issue.