Automatically Disable Wi-Fi When Leaving the Home Wi-Fi Network
Settings -> System -> System Profiles -> Default -> Tap the system icon (gear) on the right
Under “Triggers that activate this profile,” tap Wi-Fi
Select your Wi-Fi network and set it as the trigger: “On Disconnect”
Go back once, and under “Wireless & Networks,” go to Wi-Fi and set it to: “Turn Off”
(Thanks to Marcus from the TG channel)
WARNING
If the Wi-Fi network automatically switches channels, this will also terminate the Wi-Fi connection, as the channel switch is interpreted as “leaving” the network.