I've noticed a few undocumented changes in the latest 21.19 firmware.
- Clocks now have accent colours e.g. the background colour of the countdown timer is red, stopwatch is green, etc. Makes it easier to ditinguish which clock app you are currently in
- Heart rate glance now has a plot of the last 4 hours of heart rate data (in the list of glances)
- Shortcut to toggle Touch is green when enabled (was grey). Much easier to see whether touch is on or off.
Reply if you've found any other undocumented changes!
(Documented changes are here: https://forums.garmin.com/sports-fitness/running-multisport/f/forerunner-165-series/396573/forerunner-165---software-version-21-19---live)