LocalSend requires the devices to be on the same local network. TFA is about file sharing using a direct device-to-device wireless connection.
The code was added to Android with Android 4.0 back in 2011.
You can check for WiFi Direct networks manually in Settings > Network & internet > Internet > Network preferences > Wifi Direct. If you live in a city, you can probably find one or two printers in the neighbourhood advertising a WiFi Direct channel you can use to print over.