The person leaving paid work may still want to make a contribution somebody can recognize.

Wanting to be useful does not retire when the salary does. What paid work supplied, besides money, was a legible answer to the question of what you contribute, and that answer disappears on a specific Friday. The need behind it stays, and it is not vanity; it is the ordinary human wish for your effort to land somewhere that somebody notices.

Look for something with a visible result and other people in it rather than a solitary project. A regular commitment, however small, beats an ambitious plan with no one waiting on you. Being counted on is most of what was actually being missed.