After a long time of searching, I managed to find a solution to the problem of the latest versions of the flutter_blue_plus library not working properly. It turns out that additional options need to be added in Android permissions. This is what it should look like in the AndroidManifest.xml file:
<uses-permission android:name="android.permission.BLUETOOTH" android:maxSdkVersion="30" />
<uses-permission android:name="android.permission.BLUETOOTH_SCAN" android:usesPermissionFlags="neverForLocation" />
<uses-permission android:name="android.permission.BLUETOOTH_CONNECT"/>
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" android:maxSdkVersion="30" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" android:maxSdkVersion="30" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" android:maxSdkVersion="28" />Does anyone know how to add "android:maxSdkVersion" to permissions in FlutterFlow? Adding them solves all problems with this library.