If you mean legally, just check with the terms of Steam. Patreon cannot make you problems, since it would be basically the same version that is available through Patreon, so, it is only a matter of checking Steam's rules.
But it would be surprising if you had that problem. Effectively, people in Germany cannot get adult games from Steam, but people from other countries in the EU can.
Effectively, the same people that reported the problem, indicated that the prohibition was only for games with sexual content with character younger than 18, it is just that apparently Steam decided it was simpler for them to block all access from Germany to adult content, than to check.
If you mean technically, to make it available, of course that is a completely different matter.