I came into the github not expecting to like this, but you've done a great job so far! I currently use a combination of Garmin Connect (track on watch & head unit), Intervals.icu (for fitness/freshness and more obvious tracking of performance improvement over time via various power & HR metrics), Strava (for segment and route performance change over time, and of course the social aspect... and routing), Komoot (only…
Piggybacking on the top comment to mention Gadgetbridge[1] A FOSS, cloudless replacement for the proprietary android apps of the fitness trackers. It can export the data as .gpx files which seems to be format used by Workout Tracker as well.
Those who want to use fitness trackers but are put off by trade off with privacy, Gadgetbridge and self-hosted applications like Workout Tracker are great alternatives.