https://www.ifixit.com/News/113620/the-pixel-watch-4-is-the-...
FTA: "We’re also making sure that our new watches are more repairable than old Pebble watches. The back cover of Pebble Time 2 is screwed in. You can remove the back cover and replace the battery."
So the battery of the Pebble Time 2 (the watch I bought to replace my Fossil HR Collider which replaced my orig. Pebble 2) is user serviceable. I had to open my Pebble 2 because my buttons were falling off. I bought a second hand donor (Pebble OC, since I ditched my broken Pebble OC at some point) and unfortunately I failed to succeed the transplantation of the buttons. Which made me very sad.
I also very much liked you could turn the radios off on the Pebble 2. The HR was useless though. But if I want a good quality of that, I'd go for Garmin or (if I were in the Apple ecosystem) an Apple Watch.
After Pebble went kaput, I got an Apple Watch through a work reward thing and honestly it’s been solid. I turned off a lot of notifications and mostly use it for things I really want to know, some light exercise tracking, time and weather.