Yes, adult games are banned in Germany and China on Steam. I can't do anything about it, sadly.
I don't get the weird fetish/compulsion people have for playing games on Steam. Just... like... download the game on your computer and click the .exe! Are they all using the steam deck? Personally I'm glad when I don't have to tell the oligopolist mega platform which porn games I like (I like this one by the way!)