Black screen with mouse cursor on boot

I’ve installed tumbleweed without issue but on boot now I get a black screen with cursor. Help? I have an alienware x51r3

Default KDE installation?
Then it seems Plasma5 (the desktop itself) crashes on login.

Try pressing Alt+F2 or Alt+Space to get the krunner dialog, you should still be able to run other applications, or maybe even running plasmashell manually might work.

You should also be able to get back to the login screen by pressing Ctrl+Alt+Backspace twice.
Logging in to IceWM should work fine.

The first suspicion (on a fresh install in particular) would be a graphics driver issue.
What graphics card are you using? Did you install any additional drivers?

Yes, default installation. My machine has an Nvidia card in it. Since I can’t get to the X interface, is there a way to install nvidia from the command line so I can fix this?

Yes, of course.
But as you are running Tumbleweed, that’s not so straight-forward as there is no nvidia repo for Tumbleweed.

You’d need to do it “the hard way” as described here:
https://en.opensuse.org/SDB:NVIDIA_the_hard_way

You don’t really have to do it in text mode though.
I already told you how to get to a working desktop or run applications in your “broken” Plasma5.
Adding “nomodeset” to the boot options should give you a working Plasma5 desktop too.
I.e. press ‘e’ at the boot menu, search for the line starting with “linux” or “linuxefi” and append ‘nomodeset’ (without quotes) at the end, then press ‘F10’ to boot.
This will disable nouveau (that’s apparently causing the problem) and use a generic driver instead.