The current state of the game is that (on purpose) the keyboard is always p1 and p2 (so that you can test both characters easily on the same keyboard in practice mode). And the first controller that you touch after launching the game is p1, while the second controller you touch after launching the game will be p2.
So if you want to use one controller and a keyboard, the way to do that is the controller will automatically be p1 and you’ll have to set the keyboard keys for p2 how you want. Note that by default the arrow keys are for movement on p2 keyboard, but you don’t have to know that. You can use the mouse (or p1 keyboard movement keys) to navigate to the button config, then click “combat moves” to toggle it to “other controls”, then click “keyboard movement” for p2 to set it to whatever you want.