I have a Garmin Venu 2 that acts like a thumb drive when plugged in on Linux (and I assume other OSs). The files it stores exercise data as are accessible with a few FOSS tools. You can also put music on it this way. I haven't tried to extract and view sleep data to desktop, but it will show sleep scores and charts on the devices screen. I believe most Garmin behave this way when plugged in, so can be used without cloud/app interaction.
I would be interested to know if others have interesting linux desktop software or workflows for working with this data when it comes off your watch
I would be interested to know if others have interesting linux desktop software or workflows for working with this data when it comes off your watch