I am running armbian on a rock64 with a usb bluetooth adapter. Adding bluetooth devices with the blueman app is very hit-or-miss for me, mostly misses. I installed the blueberry app, which I have had good luck with in the past, and device connection has been great. Every device connects on the first try. Blueberry is easy to install because it has no arch, and it also appears to be relatively light on resources. So I would like to suggest that the devs consider including it in armbian by default.
