As everyone else has said -- a USB connection is generally sufficient.
If you're looking to see inside the FIT files, here's my (unmaintained, single-purpose) repo for doing so (a wrapper to a perl library by Kiyokazu Suto that does all the work).
https://github.com/4kbt/ParseVivosmartHR
Using it, I've been able to parse the output from a VivoSmart HR and a Fenix 3HR. I was happy to see that the HN-linked article had gpsbabel support; I haven't yet checked to see whether gpsbabel extracts all the other channels, too.
There are FIT files for 24-hr data in addition to activities; the 24-hr data are among the most interesting to me.
Garmin makes really great hardware -- I hope that this incident spurs them to open the SDK and firmware further to improve the resilience of their products.