Currently I use a Xiaomi Mi Band 5 I got forever ago, but the battery life is awful nowadays, the software is buggy, the straps keep breaking, and I don’t like the privacy connotations.
I would get a new Pebble, but I really want SPO2. Keeping an eye on HealthyPi Move
Honestly, maybe the strat is to get a Pebble for daytime use (although I would still like heart rate, which the beautiful pebble round 2 unfortunately does not have) and get a smart ring for sleep tracking.
People online recommend (ish) the Colmi R02 ring, and it works with Gadgetbridge, but currently gadgetbridge doesn’t support sending data from it to sleep as android - buuut it doesn’t look like it would be too hard to just add support myself.