I don’t know how I’ve missed this in the past–Nextcloud has a Maps app, which seems pretty slick. It will put your photos (if geotagged) onto a world map, and do the same with contacts, devices, and even data tracks in certain formats.
Installation is pretty simple, just log in as the Nextcloud admin (not the normal Neth server admin) and install the Maps app. Then sign up for a free account at mapbox.com. Once you’ve logged in there and got your “default public API Token”, copy it to your clipboard. Then under your settings, go to Additional Settings, and paste it in for the Mapbox API Key. After the next cron job runs (and everything processes, which will likely take a while), your users will see their content on the map.
It also does routing, apparently, but I haven’t yet messed with that.