I'm pretty happy with a Pixel 9 running GrapheneOS and a Garmin that I never connected to a Garmin account. I use https://codeberg.org/Freeyourgadget/Gadgetbridge instead (then synced to my computer with syncthing), and I don't miss anything from Garmin.

I'm 100% Google free, and far happier with tech that I ever was.

Gadgetbridge is great and can even recover a pretty good experience from the touch oriented watches/bands that look deceptively like smartphone equivalents.. But I think the actual smart OS level watches would need a replacement firmware first and the an implementation for talking to gadgetbridge.