I’ve been using Microsoft todo for a good while now after failing to find any decent private todo tools some while back. To my disappointment, there seems to be nothing much, perhaps with this one exception.
Everdo is one I recently ran into. It is focused on a the “Getting Things Done” Methodology, but if you are uninterested in that you could presumably ignore the extraneous stuff. It offers a local-network sync (pretty unique) as well a hosted E2EE (if I read it correctly) cloud sync service. You can see more here https://help.everdo.net/docs/sync
Privacy policy seems fine https://everdo.net/legal/#privacy-policy
It is local first, albeit on some internal database, not local files
I’m not making a note for each todo. Also Joplin seems to lack any advanced reminder functionality such a recurring reminders. But more generally and importantly and generally there’s a dozen notetaking apps that offer various levels of todo functionality, but all the bloat and extraneous functionality that comes with being a notetaking app just gets in the way. I’m only going to use such an app if it removes friction from my life, not adds to it