Remove the SIM card to ensure it doesn’t communicate with a cellular carrier. Then go into the settings for your specific WiFi network, configure IP address manually, and remove the entry for “Router” to prevent it from talking to the Internet

Sounds like you should buy a different thing. I bought one, though. None of this keyboard stuff matters to me, since I won’t even be using a keyboard with it

You can use your own keyboard with it

You jest, but we use Launch Darkly at work, and it’s the shit. Way better than our previous home grown solution. Everyone made the same joke at first, but the value is real