Although I work with Audio, I have no real clue on how audio works on Linux, despite using it since Kernel 0.97…

What I have: I’ve got a machine with normal onboard audio IOs and a BT dongle. It is running Ubuntu Server.

What I want: I want it to take the analog signal from LineIn and forward this to a BT speaker linked to the BT dongle. This should preferably run like a service, so it autostarts when booting the server.

Any idea where to start, which programs and systems to look for?