Well the gadgetbridge comment is not really true.
It can’t pull activities from Strava, runkeeper, or similar or push to them. Syncing across services via APIs or Heath Connect stops it from really being a proprietary watch software replacement or a google fit replacement as they all do that and it is a core function because people want to use the apps they want to use. For example, lifting tracking from Progression or similar which other apps like gadgetbridge or strava just aren’t made for. It doesn’t have the functionality built in to cover every activity set.
GPX is extremely limited and is only GPS data, not good for fitness trackers as they track all sorts of activities. TCX or FIT are better, but of course managed by Garmin. There isn’t really an open alternative standard. I guess the closest we come is the Health Connect API which is completely local interoperability.
And then you have Blender, Krita, OBS, VLC, bitwarden & Let’s Encrypt.
But tons of corporate contribution to big open source projects so it is sometimes grey.