Theoretically, practically, the Garmin connect developer programm is only open for businesses and not hobby projects. From my past experience this is also enforced, no hobby projects.
I have also experienced this. It’s very frustrating that my own data, while available for download on the site, is not available via API
There are a few usable libraries now from folks who have reverse engineered it. I've used https://github.com/matin/garth successfully, there should be libraries available in most other popular languages
That’s really handy, thanks
From my past experience (during COVID when everyone was trying to get access to do hobby projects) they were providing access, you just had to email nicely and ask. Maybe that's now changed again, I've not tried since.