How to force enable bluetooth on Karoo?

I have a sideloaded app on the karoo which receives values from a BLE device for display in a custom datafield. It is CGM data which is very important for me and other Typ1 Diabetics. More information can be found in this thread: https://support.hammerhead.io/hc/en-us/community/posts/5105740186267-Feature-Request-Custom-data-field-CGM-Data

But I cannot find a way to enable bluetooth in the settings - I think it used to be there in older OS releases for the original Karoo. Dunno about the Karoo 2 which I currently also have. 

Everything works fine when I connect a BT headset - as soon as I switch that off, apparently the karoo disables bluetooth altogether and the app cannot receive any more data via BT.

How can I force enable Bluetooth on the karoo?