FOSS Garmin Bike computer apps

I’m wondering if there are any good foss apps for connecting to a garmin bike computer (520) to transfer GPX files?

I used to use Komoot to generate my routes, and then their garmin app would download them from my account. This isn’t very foss, so I was looking for some better tools to make this work.

I was planning to use OsmAnd to create the route file, but then after that I would have to use Garmin Connect to transfer the file. (and with storage sandboxing, that would be very fiddly)

Any tips?

(also sorry, don't know how to crosspost)