Sadly, no. Itch doesn't really allow NSFW sales ("technically" they do, but payment processors don't and I don't feel like risking account ban there). I won't even attempt to get on GOG, I probably won't be accepted, hearing that more known developers don't.
So unless Steam implements proper age checks to comply with local laws or there's a platform I can release on without tax and legal issues, there's no option for now.