Garmin watches seem quite open even without that. I have all my data syncing to influxdb every 15min for a Grafana dashboard and it works great.
In background I also have Withings scale sync the measurements a couple of times a day to Garmin.
Probably the reason why Garmin watches are well supported by GadgetBridge
How do you sync the data out of Garmin? Something like https://github.com/matin/garth, or syncing directly from the watch?