For the time being, Garmin has not published a changelog. Nonetheless, multiple community members report that they have started receiving v21.25 despite never enrolling on Garmin’s Beta Program. Thus, we suspect that System Software 21.25 will receive an official release within the next day or so.
The new update should bring over two-dozen new features to the Fenix 8 series, including Battery Manager, Course Planner and sleep monitoring improvements. Also, the volume of bug fixes that System Software 21.25 brings to the table should push its changelog beyond 100 lines long. Garmin will issue the new stable update in batches as an over-the-air (OTA) download.