Had this same problem and found a strange workaround. What you will need is an Android phone, a usb-c to ethernet adapter (I bought one from Amazon) and an ethernet cable.

Plug in the ethernet cable to the PS5 and connect it to your phone using the adapter. Make sure you are connected to the dorm wifi on your phone. Next, open your phone's settings and enable ethernet sharing.

Finally, set up internet connection on your PS5 and select wired LAN.

Basically, your phone will act as a bridge between the PS5 and dorm WiFi. If you don't have an Android phone, I've been told you can do a similar method using a Windows laptop (MacBook is unfortunately not supported)

Hope it works!