@advocatux Thanks. Yes, I was aware I have to add the "bluetooth" policy group to the .apparmor-file:
{
"policy_groups": ["bluetooth"],
"policy_version": 16.04
}
However, I probably got confused: It seems that the AppArmor-configuration only gets adopted when the version number in manifest.json is increased (I don't know if this bug report is related).
Anyway, with this .apparmor-file and after increasing the version in manifest.json, the error ("Cannot find a running Bluez") is gone.
@Flohack
I this case, adding
"template": "unconfined"
to the .apparmor-file did not seem to be necessary to get Bluetooth-access. Thanks for the hint about running apps as unconfined anyway.