Talk to IT department?
See if you can register a computer and then input that registered IP into your MiBox?
Buy a cheap wifi extender, register that through you computer. Hardware that with your MiBox with a cheap USB Ethernet adapter?
Check with your campus Help Desk, they should have a policy for media players and their network. Our campus uses WPA2 for authentication which doesn't work well with most devices, they setup a secondary hidden wireless that uses MAC address authentication. Same issues with gaming consoles.
Have you considered a "travel router"? It's what business travelers use to connect their streaming devices to hotel wi-fi. Basically, it takes the wi-fi signal, repeats if to your devices, and you use a phone or computer to complete the sign-in process. Then your streaming devices can use the wi-fi network.
Brands include HooToo, ZyXel, RAVPower, etc. Cost is usually about $20-$30.
Would ‘web browser for android tv’ work? In play store...
Chromecast devices had the same issue, here is a link to a how to https://www.howtogeek.com/195762/ask-htg-how-can-i-use-my-google-chromecast-in-a-hotel-room/ . Scroll down to "Circumvent the Splash Screen by Cloning Your MAC Address" section for the best option.
Do you have a browser installed? If not, can you temporarily get a network connection on it some other way (tethering your phone, creating a network from a computer, etc) to load one on and see if that works? Might need to plug in a mouse since most browsers aren't dpad optimized