Air Drop
I have an iMac running Big Sur and a MacBook Pro running High Sierra (too old to update the OS). Air Drop worked fine when the iMac was running Catalina but since updating to Big Sur the two devices do not see each other. I have tried all of the fixes on this website but nothing seems to work. I have to copy items to a memory stick to transfer files between the computers.
iMac 21.5″ 4K, macOS 11.4