Osmand+ is the pro version of Open Street Map which has great trails.
It’s free via fdroid on android.

You can look into Organic Maps, it’s FOSS and made for hiking

You can get it all on open street maps, even you can contribute to the map too! Like adding a missing trail or campsite, points of interest.

Don’t use it for hiking but seem to remember it coming up in that context: Open Street Maps. AFAIK it has PC apps, android apps (osmand, organic maps etc.) and web. I use osmand a lot for maps, POI’s and navigation. Organic maps is great too. Simpler and more polished.

Height data: http://www.viewfinderpanoramas.org/Coverage map viewfinderpanoramas_org3.htm

Maps: https://www.openandromaps.org/en/

deleted by creator