Weirdly, as far as I can tell, nobody has ever made a USB C Bluetooth dongle. There are Bluetooth audio dongles for USB C that connect to headsets on their own and present as USB headsets to the computer (meant for PS5?), but no actual USB C Bluetooth dongles.
I guess the presumption is that anything new enough to have USB C will have built-in Bluetooth.
Means I currently have a USB A Bluetooth dongle plugged into a USB A to C adapter in the side of my MNT Pocket Reform, which sticks out a bit too far.
(If I'm wrong on this, please let me know.)