I geocache and hike a lot so there's one app that is fantastic for this, c:geo. I can import my trail map via gpx format, highlight the route, and download the geocahes before I hop on the trail.

https://apt.izzysoft.de/packages/cgeo.geocaching

I've also been messing around with Trail Sense, a lot of various tools for hiking. It has stuff like satellite tracking and an astronomy tool for finding where the stars and constellations are.

https://f-droid.org/packages/com.kylecorry.trail_sense

For exercising, I use an interval timer, I find Timer does this the best

https://f-droid.org/packages/io.github.deweyreed.timer.other