The title is misleading at least, to compete with garmin you need the similar offering, with swimming/waterproofing being the huge outliar here but also the ecosystem and like it or not features like the notifications. Very valiant first effort for sure but after 6 years with a Garmin Fenix still holding 90% of its battery (and being able to replace it), I'm not their potential customer.
Can you analyze the data your watch and body generates locally using FOSS without uploading it all to surveillance capitalists? That'd be the true alternative.
I by now often see the term "surveillance capitalists"/"surveillance capitalism" on HN.
While it is a great thing to fight surveillance organizations, don't forget that communist countries had/have (for the latter: People's Republic of China) much worse surveillance in place.