maps.earth is a planet-scale installation of Headway, but you can easily set up your own server on a smaller scale for your own personal use by running just a few commands.
This is the first I’ve heard of Headway, but I love their mission:
The Headway Project was born out of a frustration with the need to send current and future location data to a corporation in order to figure out how we’re getting from A to B. Offline-only maps apps can be frustrating to use, and sometimes suffer from performance problems, poor data coverage, or other technical limitations.
Headway aims to remedy these issues by bundling industry-standard software into a web app that’s easy to set up for yourself or your friends. No need to send your location data to anyone you don’t trust, not even maps.earth.