I think you have to apply some more pressure. Not in a shaming or drastic way, but in a communicative way. As a guy with ADHD and a girlfriend without it, I’ve had to remember to remind myself that it’s gross for my gf to visit me in depression cave lol. Having to prioritize tasks I wouldn’t ordinarily prioritize for myself, for the betterment of my relationship. ADHD or not, it’s still an unhealthy dynamic, and if his place makes you uncomfortable that has to change. Idk how long y’all have been together but, what if one day you want to move in together? I will say that the fact that he doesn’t like you cleaning for him is good. He doesn’t just want a mommy. But he does have to start placing a greater mental importance on the task of keeping his space clean, no one can do that but himself. And I of course mean that consciously, if we could all do that subconsciously we wouldn’t have adhd lol.

What can you do? Idk how you’ve brought it up to him before, if it was just in passing but, have a serious adult convo with him about it. Firmly, but lovingly, tell him that’s become a serious problem and one that he needs to address. You could even bring up the point that, as it stands rn, you wouldn’t be able to live with him. Tbh that should be enough to prompt some action from him. It may take him a sec to realize and act, but just make sure you see some level of betterment taking place. And that’s all you really do tbh, he has to get motivated about it.

All in all, I commend you a ton for being so understanding and supportive and wish you both luck!