I was able to pair an Android 9 phone, but then it was not possible to actually connect to the 2614 (which is in handsfree mode). However, a BT headset (handsfree mode off) worked fine.
Adjusting the volume on the phone with a BT headset connected does not work. The audio level can only be changed on the headset itself.
Suggestion: Pressing the physical headset button on the phone twice selects Bluetooth as input/output, on other words: Press once --> wired headset, press again --> BT headset, press again --> off (back to handset).
Also, the Bluetooth guide as linked from the Admin guide is not available at either