I have been meaning to add Bluetooth to my Linux desktop. When you’re in a country with limited availability, you’re stuck with undocumented/unknown stuff sold on the internet.
Luckily the dongles that have the CSR 4.0 chip are widely available. Although many of them are cheap clones and they may not work on Linux. So it’s a minefield.
But I got lucky. This item worked fine with Linux 5.9 and 5.4.
You know it’s a good day when your cheap Bluetooth dongle works out of the box on your Linux distro.