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I Was Wrong About CoMaps.. - BlinMaster
(peertube.wtf)
Cooperative community open-source fork of Organic Maps, an offline privacy-respecting not-for-profit OpenStreetMap GPS app for your phone.
Also, if you want to toggle between online and offline maps and don't care if the project is open source, then GuruMaps does this. (And if you hike the contour lines are more detailed with a smaller step between them when you zoom in)
For just online, like with a desktop, then Cartes is an option but they are still adding languages so some things are still in French:
https://cartes.app/