The space bar keybinding does not always work.
Pressing space after having attacked does nothing, except if you play (after attacking) a card that has an effect that requires you to target a friendly creature, for example a creature like Elvish Infuser or a spell like Grudge Match. Then hitting space correctly ends your turn.
For passing, it only works if you defended the first attack. Then, you can press space to pass subsequent attacks. The first attack is impossible to pass via keyboard.

Possibly not a bug, but in my opinion rather unintuitive is its interaction with attacking. Hitting space always results in all creatures being made ready to attack. Even if you’ve selected only some of your creatures for attacking, the keybinding selects all, rather than triggering the Attack button, which I would expect … binding space to always trigger whatever the button displays would make the most sense to me. But at least how it is now, you are prevented from accidentally ending your turn with space if you haven’t attacked yet, so I’m torn on that.