https://gadgetbridge.org/

This is where I'd start

are there any decent wrist watches that respect your privacy and don't send all the dam data home?

I've heard Garmin is decent, and Pebble is coming back

https://repebble.com/

there are different approaches to this, but some of these links should help:

Hardware:

https://banglejs.com/

https://pine64.org/devices/pinetime/

OS: https://asteroidos.org/

Gadgetbridge:

I personally use a garmin, which is paired to gadgetbridge

DIY: https://open-smartwatch.github.io/

Pebble has an open source OS and companion phone app.

It's made for developers, tinkerers, and tech enthusiasts. There are many community made apps and watch faces available in the phone app, and fairly good documentation and examples if you want to make your own.

https://lilygo.cc/products/t-watch-ultra

There's also a Plus version.

Also: https://open-smartwatch.github.io/

If you search for "ESP32 open source watch" there are quite a few out there.

I guess nobody here knowing about "lilygo t watch" which u can buy on aliexpress it based on esp and entire firmware can be recompiled modified from source code in github https://github.com/sharandac/My-TTGO-Watch It can integrate in gadget bridge too

I have a few Seiko watches, a Citizen, a couple Casios. All of which respect my privacy.

I used a pinetime for a bit: https://pine64.org/devices/pinetime/

AsteroidOS is a linux based replacement for wearOS (android for watches) which is FOSS and removes all the google privacy issues.

https://asteroidos.org/

Mechanical ones, sure. :)

Daaaaaaaaannnngggg...

https://www.citizenwatch.com/us/en/product/CC4075-50L.html?cgid=mens

+1 for banglejs. Been loving mine

I suppose you're talking about smart watches?

Not to sound stupid, but it really depends on how smart you want the watch to be. From connectionless firmware device to fully-featured Android. +1 for gadget bridge either way.

I have a Fossil Hybrid, that combines physical hands with a 2-color e-ink display. It can't do apps, but it has standalone timers, notifications, media control, pulse/oxygen and step counter. I personally don't need more. It's cloudless and lasts a week.

If you need full Android/WearOS check AsteroidOS and specific ROMs. Hardware tends to be on the older side here.

The only thing that's hard to do is sleep tracking. That tends to rely on proprietary algorithms and cloud compute a lot.

sensorwatch.net is the only one I'd want. Note it doesn't have any data communications to speak of. It's an old fashioned digital watch with some cool features including software thermocompensation for accuracy within a few seconds per year. And it runs on a regular coin cell for a year or so, not a stupid nightly recharge like it thinks it's a phone.

I've heard of the SQFMI Watchy and the Bangle.js but I haven't used them myself.

I've not played with it and don't know much about it, but maybe the pinetime?