I am using the i3 window manager on Debian Stretch and for some reason I can't open a terminal via Alt+Enter or dmenu. I have tried the default terminal and gnome-terminal. I have also tried removing and reinstalling i3. TTYs still work.
That's because the "default" terminal in i3 isn't actually a terminal it includes, it calls one of a few commonly installed terminal emulators like xterm and urxvt, including gnome-terminal:
What happens when you run i3-sensible-terminal from the command line?
Edit: you can't open ANY terminal at all via dmenu? As long as the binary is in your $PATH it should open, regardless.
I fixed it by using the command sudo rm -R /etc/i3*
This caused problems with the status bar so it is not recommended