@rew0452 are there any senior centers in your area? Many of them offer programs for those with early dementia. They might also have ‘day care’ programs. Now that summer is coming, maybe he’d like to spend time at a pool.
https://pameladwilson.com/ Have I given you this url before? Members have said it’s a great resource!
Members came up with a list of activities that you could modify based on your spouse’s interests
https://connect.mayoclinic.org/discussion/activities-to-share/
Do you think he would be interested in 2-person games like Scrabble? You could have a talk with him and see what you can come with!

His brain is broken, you are trying to not only resolve the issue but make him fit into your mold of what he should be doing.

That will not work, let him be, go about trying to live your life not his.

This is a difficult journey you will need to continue to adapt to his every changing downward spiral.

You cannot make anyone happy except you, stop pushing him to do what you think he should be doing, doesn't work that way with dementia.

Sending support your way.

You mentioned a neuropsychologist- has your husband had the testing done? If yes, I recommend you schedule a return visit of just you and have them show you your husband’s testing answers and explain the details, comparing and contrasting the results with the “norm” for his age. This was totally eye-opening for me. I knew then I had been that frog in the boiling water, time goes by and without realizing it really, you make bit by bit adjustments. The testing also creates a baseline that repeat testing in a future year will provide hard data for the changes. My husband enjoyed the testing- said it was like doing different sorts of puzzles and word games.
As far as activity, I vote with other commenters to just work with what he likes and let him be. My husband, too, sleeps a lot- I read somewhere that the brain realizes something is wrong and attempts to “right it” during sleep. He used to play hours of solitaire, but can’t figure the game now. He likes drives in the country, so we go to drive-throughs (in person restaurants can be overwhelming/stressful)- Dunkin for coffee and a doughnut or Dairy Queen for ice cream or McDonalds for a shake, and then take a drive. A drive makes for easy and good conversation about what you see, memories of what happened at that spot, talk about the landscape, what’s new with the season- here the dogwoods are blooming, farm fields are being plowed. I drive by his old workplace and he’ll launch into a funny work story (have heard them all a million times, but so what- we laugh and laugh).
I wouldn’t worry about keeping him busy, “go with the flow”. We’re here for you.

In the early stages of my husband's diagnosis of Alzheimer's, five years ago, I was upset that he was napping so much. The neurologist told me that his brain needs time to rest and it's typical of the disease.
I've purchased various jigsaw puzzles for people with dementia, 16, 35 pieces, and a couple of children's puzzles (with appropriate themes, not babyish), 100 pieces.
My husband's gone through a number of phases. Often when I asked him to work on a puzzle, he'd say no. When I said it would just take 10 minutes, he'd agree, then get involved in doing the puzzle and forget about the time.
The last week or so, when I sensed he was bored, I put out a puzzle and he's started to work it on his own. He seems to enjoy the challenge and has a great sense of accomplishment when he's completed a puzzle.
I play Scrabble by myself. He often looks at the board, looks up the words in the Scrabble Dictionary or makes suggestions. Sometimes I can get him to keep score.
This morning he asked me to go on a walk with him. Often, when I ask him, he refuses. Sometimes, he'll agree to a walk later on in the day.
I've found I have more success with sneaky interventions and suggestions than direct invitations. That's just where we are now.