So I've bought an Asus Bluetooth 5.0 dongle, which worked nicely without any installation on Ubuntu 16.04. After a complete wipe of my machine and a reinstall to a fresh/vanilla Ubuntu 20.04 I don't see a bluetooth dongle in the system settings.
lsusb identifies the dongle as "Bus 003 Device 022: ID 0b05:190e ASUSTek Computer, Inc.", but the 'Settings' app tells me that there's "No Bluetooth found".