I OT: I keep seeing the 'need' for a dedicated wi-fi LAN for hardware that interconnects (like bluetooth functionality, except wi-fi). I bought a cam that produces its own wi-fi signal and the cheap laptop picks it up just fine and displays the stream via VLC. A new printer does a similar process.
Can I just plug in one of these, set it to X (which?) mode and not connect to the internet?
https://www.amazon.com/TP-Link-Wireless-Travel-Extender-TL-WR802N/dp/B01CVOLGOG/
>Can I just plug in one of these, set it to X (which?) mode and not connect to the internet?
You probably can -- I mean, most routers work without internet access. You could also use a pirate box (https://piratebox.cc/).
That looks suspiciously like the thing that Theresa just installed to get signal to her office (It's a TP-Link range extender). I don't think it needs any internet connect. It was pretty plug and play (though she plugged it and played it, so you'll have to ask her for details). I think it was a simple authentication and then it connects you to the router. If I go to my computer and connect to the router using the bridge, I can still access the router on it's normal IP and the router sees my MAC and IP, not that of the bridge.
So as far as I can tell, connecting to a router via the TP-Link extender is pretty much identical to connecting directly to the router except you're on a different SSID (but same password as the router and the SSID defaults to YourRouterName_BOOST)