I don’t know if you’ll read this so long after you posted. But just in case:
We ADHDers famously have two natural modes of motivation. There’s the hyperfocus, or “holy cow this is so awesome I have to do it now and keep going” mode that you fondly remember from your early days, and a crisis or “holy cow, if I don’t do this now I’ll lose something I can’t live without” mode. The latter hurts to activate (though less so on appropriate meds IME…but you can’t force someone to take or adjust meds) but works.
The difference between what I love and what I just hyperfocus on is that if it’s love, the crisis mode can be activated relatively easily (but still not without pain and drama) to preserve what’s loved when hyperfocus on it has been lost. Also, it is possible to bring back hyperfocus in certain situations, if I think about why I committed to what/whom I love in the first place. But that may not happen until after the crisis has been processed and the butt-saving plans have been made.
One reason why passion might be lost in the first place is time blindness, which is not just about being late and procrastination: for me it’s actually strongest with respect to the past. I don’t remember good times in the past like they were yesterday, I remember them like they were a whole other lifetime ago. Even regarding things and people I love. By default, they pale in comparison to what’s on my mind, especially what’s bothering me, in the present. And the negative of the past only comes up in the context of the negative of the present: it’s forgotten and even forgiven until I’m unhappy now, and then I remember all my accumulated million reasons for being unhappy. If I were also an other-blamer and defensive, this could be a recipe for losing everything I love!
So your spouse might need help remembering why you got married in the first place (hyperfocus mode) and/or thinking about whether his life would be one he wants to live if you weren’t in it (crisis mode). So to try to provoke the hyperfocus mode, propose a date to do favorite things together with no strings attached. This, if successful, can bring back all those long forgotten good-time feelings and help him appreciate more what he has. Then, if you’re lucky, crisis mode will kick in on its own: “holy cow, I could lose all this.” If not, he will need a nudge, but a patient and non-blaming one – I statements, not you statements – that can remind him of what he could lose and how it might not be easy to find something better.
And failing that (but hopefully not) get shrinks and then lawyers. Yes, I’m bringing up the worst case here. But worst-case thinking allows me to use crisis mode to avoid the worst consequences of future blindness. Maybe, like a kid (and emotionally we usually are like kids), he might not take a threat seriously until it is concrete and imminent: if you have said “I’ll leave you” before and not gotten lawyers, he may have learned to ignore it as a false alarm. Try the shrinks before the lawyers, of course. My mom did that with my probably ADHD dad. Sadly it didn’t work because my dad insisted that only my mom had a problem. To this day he still does. But hopefully your spouse hasn’t given up and isn’t staying with you because getting the lawyers is too much of a bureaucratic headache for his ADHD, and so some way or another can be motivated to put his butt in gear and save what he really loves!
Best of luck, and patience. Our spouses need it because we suck at it. 😉