I have a Gear S3 that I like using for Samsung Pay. I had initial trouble with it when I first switched to GrapheneOS. The app on my phone wouldn't let me login and would complain about unauthorized changes to my phone, I believe because it fails SafetyNet. I was able to install an older version of the app (Samsung Pay 188.8.131.5206) that allowed me to add my cards to the watch and then I updated the app after signing in. I think there was a recent change with an update because all my cards were removed from my watch and reinstalling the old version doesn't work anymore, complaining that the app needs an update to continue.
Has anyone found a way to successfully use Samsung Pay?