If I was choosing a Smartwatch from a cold start I would first check wearables supported by Gadgetbridge, here is a page Wearables - Gadgetbridge. this approach avoids having to use the (proprietary ) app associated with most / all Smartwatches … it is the use of such app which tends to phone home all your data.
If you saw a device that might work for you, then you might double check it for user experience on the forum.