My G6 came with OnStar, XM and every other damned thing you can think of. Except for Bluetooth.
It's easy enough to swap the VCIM (communications module) with one that came equipped with Bluetooth.
The deal is, in order for the Onstar system to "go green" and function correctly, the VIN has to be programmed into the replacement (salvage, in my case) module.

The VCIM is separated into two circuit boards. A large board with all the vehicle connectors and the Bluetooth; and a small board that includes the cellular antenna connector and a GPS antenna connector.

The question is... can I swap in the cellular board from my old Non-Bluetooth VCIM and have everything work, or is the VIN and cellular IMEI stored on the other, larger board?

I realize that this is a long shot. But there is nothing on YouTube (or anywhere else within Google's reach) that addresses this, specifically.

Note that I don't have my OnStar account activated. Never have. I just don't want any surprises.

Read this entire article and see if this helps. One parts says that the light will turn red due to the mismatch parts but everything will still work. It also says that there is a bluetooth dongle antenna that is needed.
https://www.christopherpric...r-cadillac-2847.html

I've read that same article. I'm just hoping that swapping circuit boards around might make everything "happy", without going through the whole programming thing. (My OCD is kicking in. I hate for stuff to not be "right".) But if I have to put up with a red light, so be it.
I also ordered the bluetooth antenna. I didn't realize that the VCIM module I bought was also going to come with one. So now I've got two.