UR22 Production Bundle and Mini MIDI keyboard?

I’m looking into getting the UR22 Production bundle for my son as part of his Music Technology course. Can anyone recommend a 25/32 key MIDI keyboard to connect into it? And also help me understand any connectivity issues please.
I appreciate the bundled mic gets connected through the front and the keyboard through the back. But most of the mini keyboards I’ve seen on the internet say they’re USB. Whereas the UR22 appears to just have the MIDI ports for connection. So I’m guessing the USB keyboards are out.
Apologies in advance if this is a really basic/stupid question.