Apparently, I should have add YMMV (Your Mileage May Vary) at the end of my post.
My machine is also a System 76. I ordered it with Ubuntu installed but almost immediately removed the Samsung 970 EVO Plus it came with and did a clean install of Linux Mint 19.1 on it (it now has 19.3). I also installed System 76's driver package on it after installing Mint. Apparently, this was before System 76 adopted Core Boot (sometimes, I get lucky, considering the complaints I've seen about Core Boot).
This is the pop-up window I get when I click on the BT icon in the panel:
Note that the switch in the upper left corner of the window is grayed out, indicating that it is switched off. I can switch on and that setting will be retained through multiple reboots, then switch it off again and that setting will also be retained.