The first Oura ring has its own firmware which will be updated via Bluetooth whenever the app introduces a new version.
Firmware Update Specifics
When a new version of the ring firmware is available, the app will prompt you to update the firmware when launching the app and syncing the ring. For the firmware update notification to appear, your phone’s Bluetooth must be enabled, and your ring’s battery level must be above 50%.
If the firmware update is unsuccessful, please visit the troubleshooting section here for help.