Okay, but does fulfilling commitments you've made to people hit your brain as Necessary? Because if so, volunteering can be great for that if you need a structure that will make you get the fuck out of the house, showered and presentable to the world, and at least occasionally encounter other human beings, on a regular basis.

Example: my father does a lot of volunteering at the Desert Botanical Gardens. Like, signs up for regular shifts as a docent, but also stuff like event captain for keeping volunteers organised and on task and such for special events, and so on. He is faaaaaar from the only older person volunteering there to keep busy in their retirement. And there are A LOT of organisations you can do that kind of volunteering for! So, yeah, if it DOES work, Many Possibilities Exist. If it doesn't... eh, fair play. But worth mentioning, I figure.