The http://192.168.12.1 interface has NO user-settable anything!
Whereas the user manual (https://www.t-mobile.com/support/public-files/attachments/t-mobile-arcadyan-kvd21-user-guide-english.pdf) shows a WiFi section.
I was able to set my wifi using the phone app (which is quite buggy), but I hate to use the phone for anything that needs a lot of typing. I should be able to do everything on my desktop computer via the Gateway Web page.
The phone app filled in my passwords, but the submit button was inactive until I added a 1 at the end of the password and deleted it. This is really frustrating.
And so far, the upload speed is just 2 Mbps. Too slow to upload a 20 GB video to YouTube. So I will probably have to return this to T-Mobile and keep Xfinity. Alas.