It is possible to enable AirDrop in a wired network even when your Mac is not supported. After restarting the Finder, Airdrop will appear in Finder’s navigation bar.
defaults write com.apple.NetworkBrowser BrowseAllInterfaces -bool true
To make the command take effect, you need to restart Finder:
killall Finder
Revert to the default setting:
defaults write com.apple.NetworkBrowser BrowseAllInterfaces -bool false
Screencast: