I think that generic volunteering might even make a person feeling worse, if they don't fit in with the organization.

All organizations have a culture.

Be strategic. Start with Meetup, find a couple of things that interest you and align with your work. Then find a role for yourself, a project that has specific outcomes and that you contribute to specifically. Have a cut off date where you either join something else, or move up in your role.

Or, go on a completely different tack and take up drumming in a drumming circle.