Garmin Connect does not show software updates for Edge Explore

Hello,

The current software version on my Edge Explore is 4.20. Connected on the Garmin website(connect.garmin.com/modern) it says that there is a new version of the software available: 5.10. But the Garmin Connect app on iOS does not show this update. In the end I am unable to update the software on the Edge Explore. That would be really useful to fix the numerous bugs that it has.

Does anybody know a way to force the application to check software updates? Or to manually update the device? Garmin Express is not an option as my computers are running Linux.

For that matters I tried on a Android phone and the Garmin Connect app does not show the update either.

Any hint would be appreciated,
Fabrice