Surface Duo is not compatible with the Galaxy Wearable app. Which watch should I buy?

[Surface-Duo-fan]

It is October 2021. I purchased a Surface Duo last month, and purchased a new Galaxy Watch4 yesterday. The problem is that the "Galaxy Wearable" app does not work (It opens to the start screen but no buttons are responsive) and that means the Watch4 cannot be used with the Duo. I just ended a tech support chat with Samsung and I was told that the Watch4 only works with Samsung devices. So: What smart watch can I buy that is compatible with the Duo? There are many previous forums in Windows Central, all from 2020, saying that the earlier Samsung watches like the 2 and 3 are compatible with the Duo. But the Galaxy Wearable app does not run on the Duo as of today, and that means the Watch4 cannot be used.