I tried signing into Unity Hub but it won't sign me in and I'm stuck on the log in screen

Have you created an account?
There is a “create account” link below the sign in button.

It takes me to this screen and doesn’t sign in.
I do have an account.

It looks like you are running KDE Plasma desktop which I don’t know how to troubleshoot.
You might ask in a KDE forum for help.
Officially Unity is only supported on Windows, Mac, and Ubuntu Linux.
I understand that KDE is based on Ubuntu so it should work.
You might try reinstalling: