Shawn does not work for Microsoft and actually does not have a lot of experience with Surface devices other than his own SP2017. I doubt he has had hands on experience with Bluetooth dongles.
There are a couple of Microsoft/Surface keyboards that support Bluetooth - which one do you have? Buy Surface Bluetooth Wireless Keyboard - Microsoft Store is compatible with Bluetooth 4.x/5 - some of the dongles out there are only 3.0. Amazon has some 5.0 USB adapters Amazon.com : usb bluetooth adapter 5.0
As for Shawn's statement about requiring the latest version of Windows 10 21H1, he is wrong. There is a new "swift pairing" function in Windows 10 that was introduced recently, and THAT does not mean regular pairing should not work (some of these keyboards work with Macs, etc.).
There are a few things that could interfere with Bluetooth pairing - but I'm not sure if that is where you are having issues. Have you tried any of the 5.0 USB Bluetooth adapters?
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