>their computer refusing to play nice with their printerYes, you reminded me of a very good point about local wifi communications:
If 2 devices are on wifi, it's easier if both are configured as clients that talk to a 3rd server (such as cloud). When both act as clients, they don't need to know each other's ip address to communicate.
The other option of configuring one of the wifi devices as a server is more difficult especially for non-techies. Now, you have an extra complication of discovering the ip address of the printer/camera acting as a "server" to receive commands. This requires a weird dance where the server device has to "broadcast" itself and you have the client computers "find" it. For my Canon wifi printer, I had to press and hold down the power button a certain way so the computer could "discover" it. For my wifi camera, I had to go the DOS prompt and enter an obscure ARP command[1]. The difficulty is compounded when the "server" device has no builtin LCD display so you're basically "flying blind" as to what ip address it got from the wifi router's DHCP.
However, the HVAC wall controller has a large LCD display and touchpad so configuring it as a server on local wifi shouldn't be that difficult.
[1] https://www.axis.com/ro/en/support/faq/FAQ2551