Sleeps 12+ hours a day. How do I motivate him to show interest in hobbies and/or activities?

You seem to want to him to behave like someone he isn't and never was. And, never going to be. If he says he's happy then just let a sleeping dog lie and move on with your own life. Yes, dementia can cause people to be that way. I wish you peace in your heart on this journey.

I'm glad you've built your own fulfilled life and his sleep schedule isn't holding you back, that is excellent. Some of the recliner crowd want their significant other with them at all times.

Your therapist has given you good advice. I'm sorry it is hard for you to watch. Do you think you are ready to move into assisted living?

Quit trying to make him into someone he's not and just accept where he is now at.
It sounds like you're perhaps in a bit of denial about his condition, which of course makes it more difficult for you to accept things as they actually are instead of how you'd like them to be.
It also sounds like perhaps he's now become an inconvenience for you and your supposed "fulfilled life." What a shame. Your husband can't help the way he is anymore as his brain is now broken.
What if the tables were reversed and it was you who had the issues he has? How would you want him to treat you and care for you?
That's the way I had to look at things while I cared for my husband for 24 1/2 years. I believed that he would care for me just as good as I was caring for him.
Now I'm not saying that at times it's not hard, because God knows it is, but as a spouse most of us vowed to take care of each other "in sickness and health, till death do us part", and while it's not always easy, it can be done to the best of our ability.
So let the poor man sleep all he wants(my husband slept 14-20 hours a day for the last several years of his life)and just let him know that you're there for him and that you love him regardless of what's going on with him. And if he's sleeping more it also allows you to get more things done and more time for yourself right? So perhaps it's a win win for you both.
I will also suggest finding a local caregiver support group that you can attend. I know that my support group saved my life while I was caring for my husband, because who better to be able to share with than other folks who know EXACTLY what you're going through.
Best wishes in doing what is best for your dear husband and yourself.

Your therapist is correct. Let him live as he wants. You cannot change the behavior of others, only your own reaction to it.

My mom had Parkinson’s disease. Do yourself a favor and further educate yourself on how this devastating disease affects people. It affects everyone differently.

Your husband is NOT the man that he was before he had Parkinson’s disease. So what if he is an introvert. There is room for everyone on this planet.

Trust me, people who are suffering with Parkinson’s disease aren’t peppy!

Listen to your therapist. She sounds like a very wise woman.

Best wishes to you and your husband.

Spending all day sleep, reading, and rewatch my favorite old shows sounds like a paradise, especially for a lifelong introvert.

My father was like this with really no illness at all, just was in his 90s, had a wonderful and happy life, and was just so ready to go. He was tired and said he longed for the "last long nap". He tried to get up and about to keep Mom happy but had no appetite for food, and just longed to rest. He talked with me often. I had many patients as a nurse who told me they felt the same and that they slept more and more, ate less and less, and just could not be honest with families that they were FINE with this, that this was OK. The families just couldn't hear it; so the nurses did.

My husband just with Parkinson’s and no dementia whatsoever but several surgeries, cancer, pain and the most active person few years ago does not do anything either.
Sleeping a lot, reading and watching TV, although he watches lots of educational shows and is involved in everything from finance, politics etc.
I do not suggest anything. He had physio for almost 2 years,
3 different therapists, each promising improvements,
if anything it is worse, so this man who exercised two hours a day a little over 2 years ago does nothing.
I accept how horrible Parkinson’s is. It is cruel disease, slowly leading to total destruction of motor skills.
I can only imagine what it feels like knowing what is happening and there is no cure, no hope for it, or any alternatives.
We saw every specialist, none offered anything anybody with little knowledge of general health wouldn’t already know.

I can see why he'd be willing to move to AL. They nag people there a lot less.

Know how you feel. My hubby has dementia and many medical problems. I'm full time caregiver. Just the 2 of us at home. He sleeps more than he is awake most days. It does get frustrating, as one friend commented about her husband, she felt like she lived alone. The one time he is awake is to go to the bathroom st night, doesn"t go back to sleep for several houra, and I'm awake the rest or most of the rest of the night. When he is awake mostly watching TV also. He also was never a very social person either! Does better cognitively when he is at home, over when he is hospitalized or was in rehab. His daughter is a half hour away, works , comes after work once a week so I can grocery shop. Thinking about some relief so I can do something, beside go with him to DR. Appts!