Apple - How do I preview a Live Photo using the keyboard in Photos.app?

If you have a 2016 or 2017 MacBook Pro w/ Touchbar there is a small icon which plays the Live Photo.

Unfortunately I haven't found a solution for MacBook users w/o Touchbar so far...

I don't know how long this have been the case, but now you can use option ⌥ + Space combination to start playback on a Live Photo or video (works on Catalina)