So this is completely on me:
I installed Arch
I installed the plasma desktop without any additional programs
I installed sddm and told it to launch plasma desktop
I rebooted
And it did what I told it to do perfectly:
I'm now within plasma desktop.
I have no terminal emulator installed, so no way of accessing a command line from within the GUI.
Whenever I reboot, I get put back into plasma desktop.
I tried to switch to a different tty with Ctrl+Alt+F-keys but that key combo seems to be used for additional desktop sessions instead (shows me the sddm login again).
I tried creating a shell script that launches pacman and installs a terminal, but I can't, since I don't have a text editor installed.
Help!
[Edit: Solved. I was able to go to a different tty after disabling function keys]
I see you got it fixed and other people told you about chroot, so you're all good for now. FYI, next time you install, follow the wiki. There's a package that they tell you to install during the initial setup that includes all the basic things you'll need, like terminal, a browser, etc. If you skip that then you will definitely have issues like this.