After I wrote about this topic 2 weeks ago in my last post, I made a few changes to my setup. First of all, I made some changes to GPXExport so that it would better fit my needs. I collected this changes in a new repo and named it WorkoutExporter. The main change is that WorkoutExporter writes the GPX in a more readable manner1.
I also remembered that I experimented in the past with tapiriik in the past. I forgot about it because I did not have a fitting use-case then. Tapiriik supports syncing with Dropbox. I tried it for a few days and it synced perfectly the workouts a wrote to a specific Dropbox folder to Strava.
I think this could be a good alternative if one does not want to utilise git for this.