I use Grapheneos, and recently I discovered Health Connect (because of an update?). I mainly use foss apps and apart from openscale I’m not sure what I could use it with. Is anyone using this with another free app? Is this not (yet?) Useful for open apps?
As far as I know health connect stores data locally on the device and does not send anything to google.
The gadgetbridge project is currently working on supporting (optional) network access, so integrations like this should become possible.