Worth a look at Coros. I find their battery life and product support to be much better than the garmin watches I’ve owned. They even added maps as an update for existing watches when they could have forced people to buy a new watch for that feature. Not FOSS though.
If there was an open source GPS watch that could last long enough with enough accuracy for my workouts, I’d be all over it!
I’m surprised by this decision, since Ubuntu’s strength is stability and by extension, friendliness to new users. Imo, a better move would be to ship a separate “unstable” release with non-LTS kernels.