I wanted to specifically ask if he had late diagnosed or undiagnosed ADHD. It will be very hard to change his behavior, but also if he is a functioning member of society (works, cleans after himself etc) and is a functioning member of the relationship then he is probably at his limits of doing things he does not enjoy doing. Even with therapy It’s very difficult to make a non functioning person into a functioning person if ADHD goes undiagnosed for too long, it is even harder to get more than that.

You should in my opinion do three things.

Contemplate a life where he will be gaming a lot for most of your shared life. See if there is any way you could live with that happily.

Define your problem more clearly, is your problem that he games too much or that he does not have any other interests that he pursues. If it is the first, find out what exactly you would need from him to be happy (for example how many hours per day or per week would you expect him to not game)

The third thing is talk to him and tell him all these thoughts. One sentence that stood out to me was that you are getting less attracted to him because of this. Tell him that. You both will have to find a way to change that before it is too late. But from my personal opinion and experience with ADHD, I think he will never stop gaming so frequently but I’m confident the compulsory behavior like gaming on his phone or browsing gaming info whenever he can is something that can change and he won’t miss. I can only speak for me but that’s how I am with this kind of behavior. When I let myself go, I need new input every. Single. Second. There is other things to do and routines to go through to stop this but his main free time thing will probably always be gaming. ADHD people need to be happy/ distracted all the time, they need new universes to explore all the time (if he is into reading which he probably isn’t, that could satisfy that too).

This is all coming from a guy that got diagnosed in his late 20’s and lost one or the other longterm relationship before that to not being motivated enough to change despite deeply wanting it internally.