My Galaxy watch is running R815USQU1BRJ3 firmware, from last October. According to this page there have been 3 software updates since that version. The Most recent one being rather significant because it updates the UI. I have tried every method I can find or think of to get it to update. I've paired it with Samsung Phones, Non-Samsung Android Phones, and iPhones, and even run in in standalone mode. It doesn't matter if I check for updates in the app or on the watch itself, it just tells me it's already running on the latest software. I've factory reset it more times than I can count.
I'm running out of warranty on it and I want to get this issue resolved before it becomes an expensive, buggy paperweight.