I use an extension with my students to communicate via Bluetooth with App Inventor: https://makecode.microbit.org/pkg/laboratoryforplayfulcomputation/pxt-blockytalkyble
I notice some problems in certain conditions:
On a device running Android 9, everything works correctly, in debug mode, and once the Android application is installed. With Android 10 on the other hand, the scan of the Bluetooth devices does not work with an installed program whereas in debugging mode on App Inventor, it works.
Another problem, the extension does not seem to be compatible with the micro bit V2 card. If it works with a first-generation card, I get the error code 927 with a V2 card.
Thanks for your help.