Mapus is an open source tool to explore and annotate collaboratively on a map. You can draw, add markers, lines, areas, find places to go, observe other users, and much more.
Great idea. I remember once I was searching for a place to go with a. Friend and this would have been useful.
A self-hosted version would be quite useful
Polar Habits
App Access Matrix by Stitchflow
Digger.dev