Yes, including the 18-karat gold model.
https://www.engadget.com/the-original-apple-watch-lineup-is-officially-obsolete-083825819.html
Your comment sent me digging. I had no idea that they could still function. I thought they were lost to time (lol), but apparently Google gave an update to the official app so the Rebble project could keep supporting all the functionality of the watch. Looks like it’s Android only, though tbf Pebble always did have significantly more functionality on Android than iOS. But if it would work on iOS, I’d dig out my Pebble right now.
I think you can technically still use Pebble on iOS, but I’m not sure how. The previous owner of the watch has been using it with his iPhone 13.