Wanderer is a free open source Strava-style platform which lets you store records of your walks and trails online and share them with others. You can record trails directly using GPS data, or you can import existing data from Strava and Komoot.
There is more information on the official website at Wanderer.to ⧉ and there is a list of public servers you can join ⧉ on the same site. If you just want to give it a quick try there is a demo server ⧉ which automatically deletes data after people have tried it.
If you’re a techy person, you can self-host your own Wanderer server using the installation instructions here ⧉.