Can I force AirDrop to work on High Sierra without WiFi hardware?
Please note that my answer has not been updated after it was made clear that the Wi-Fi hardware had been disabled/removed.

You can add AirDrop to Finder favourites by going to Preferences->Sidebar and ticking the box next to AirDrop.

If it's missing from there, you can reset the Finder settings by deleting the following files:

~/Library/Preferences/com.apple.finder.plist
~/Library/Preferences/com.apple.sidebarlists.plist

Log out/reboot/force quit Finder to reload the settings.

The Apple support page says AirDrop is supported on 2009 and newer models