We could just form a group (much like nostr:npub17nvfw7g53nxjghyd2zg552z06cke0jc0k69hj7ns7f9pw26j9kusap4u85 does for workouts) and meet weekly on NostrNests to set the weeks' goals. The timing might be tricky across different time zones, but if we have enough folks in the group we could eventually break into more local groups.

There are so many Nostr clients that I have never explored, and I bet some of them lend themselves really nicely to this kind of thing.