Bluetooth tethering or P2P connection with ubuntu linux

USB tethering works well with VIM1_Ubuntu-xfce-bionic_Linux-4.9_arm64_EMMC_V20181030, but I cannot get Bluetooth tethering working. Has anyone had some success with this, with any Linux image?

I suspect something is terribly wrong with Bluetooth, because audio connection with speaker is also useless (distorted (minced) sound).

Sharing Bluetooth P2P experiences are very welcome too. I’d like to use mobile phone as a remote for Khadas, with web (or even console) UI.