Hi not an expert here, but I saw your question and got curious. I think you are better off plugging in just a RCA Bluetooth adapter, the USB port according to the manual is an A/D, D/A with 16 bit 44.1 kHz or 48 kHz, which means you will need some kind of interface, aka. a computer, to transform this into a Bluetooth signal with whatever codec. A Raspberry pi could do the trick but you have to decide if you want a plug n’ play solution or if you want to experiment.

Unlikely on the USB-B, that would need a PC and drivers to negotiate and understand that it’s presenting as an audio device. However with its RC out and adapters, you can get bluetooth transmitter/receiver units?

I don’t think so. It sounds like you are trying to connect two input devices. The USB on the AT is supposed to be for interfacing with PC software to record LPs.