"I have figured out, that the problem is bluez in Ubuntu - it simply doesn't work for HDP since bluez 4.101. Unfortunately till now I could not figure out why. Even the test-health script from the bluez-stack doesn't work in Ubuntu. After that I have tried Ubuntu 5.10 which uses the recent version of bluez (bluez 5.38). The test-health script from the bluez stack doesn't work here too. So I have tried another distro: manjaro. Surprisingly, the test-health script worked here out-of-the box. Another thing I have tried, is to use the recent bluez compiled from source in Ubuntu 15.10. It doesn't work either. So it seems to be some problem of the generic Bluetooth driver in Ubuntu. So for now, I have ported the bluez-plugin of antidote to the recent version 5 of bluez because this works under Manjaro or Debian. But the port does not work anymore with bluez 4.x. I will add eventually a configure-switch to be able to choose between the different bluez-plugin versions. Is someone interested in the port?"
In short: the problem here is almost certainly the Bluetooth implementation in Ubuntu. So just use Debian or any other distro like Manjaro (Arch based).
Best regards
Michael