Hi @Anke
Thanks for the updated app.
I've used the first app and BT connectivity is successful between microbit and Android ver. 12 mobile.
(Refer 1. app - built on AI2 build server)
Please see the screenshots:
Starting the app
Device details - Scanning the BT devices
Selecting device and Connecting
Connecting the devices
Successful BT connectivity
Successfully message sent from microbit to mobile
Thanks & Regards