Here are some suggestions that I hope will help you:
First of all, carefully recall what the elderly are interested in. If he can't remember, try to talk to him about various topics and see if there is anything that can excite him. Find his interest or excitement, create some conditions, and unconsciously let him do something, maybe he will gradually like it.
Second, let the elderly feel needed by others. After all, being needed is also a basic need of people, from which we can feel our own existence value. In my yard, an old man lived for more than 90 years and died not long ago. I haven't talked much all my life. When I was young, I was a carpenter, and later I was an official cadre with some status. In my opinion, he has only one hobby and is willing to do things that are beneficial to others. He got up earlier than others, and by the time you went out, he had cleaned up the environment. The sewer is dirty and the water is blocked. He will spare no effort to clean it up. Your flowers can't grow well. Give them to him, and he will give them to you when he is well.
Learning to praise and appreciate their hobbies will make them feel very happy. That's my grandfather. After he retired, he played with a brush quietly, leaving no one to take care of him. It's been 20 years now and I'm still insisting on it, and I've participated in many art exhibitions. As a junior, I often ask some related questions and ask the elderly for some works, which is what I can do.
Fourthly, I believe that many elderly people, for various reasons, are thrifty and unwilling to spend too much on hobbies. Whether you spend your own money or let the elderly contribute their own money, you need to make them feel that the money is spent "yes, it is spent well."
No matter what hobbies you cultivate, the unconditional support of your family is the most important thing!