Alright, where's my replacement once my current Fitbit dies? What company makes a watch that tracks steps, heart rate, sleep, spO2, notifications, is generally water resistant (light swimming) and has a battery that lasts ~5+ days? Bonus points for open firmware/hardware that doesn't require me to design my own apps/systems for each of those items. I don't even use most of what my Versa 3 can do, but I know it won't last forever and I'd at least like an idea of where to go if/when it breaks down.
Check out Withings. Not open, but they are pretty good on respecting privacy and check the boxes you want. withings doesn't do the full screen app stuff, but it's a good watch with all the smart features.