Originally Posted by
dojero
Network manager is not installed. It has nothing to do with my wifi drivers. As I said, Kali LXDE's WICD works perfectly. Network manager doesn't exist on the Mate Kali system. More important, wpa_supplicant doesn't exist. This is crucial for wifi that uses WPA security. Even if Network Manager were there (it isn't), it wouldn't be able to work without wpa_supplicant. My wifi is a Ralink RT3290. But again, this is completely irrelevant.
For those interested, the solution was tedious. After booting in any live Debian distro, I ran aptitude download <package name> for wpa_supplicant (and any of its dependencies you don't have). I then mounted the hard drive of the computer I was using and copied those deb files to that drive. Then booted back into Kali Mate 2017, mounted the hard drive, and copied the deb packages over to the Kali live drive. From there, I installed them using dpkg. Once that was done, wpa_passphrase and wpa_supplicant worked and a connection to the wifi network was made.
If anyone needs more details, reply here.