Disable the sliding transition between photos and videos in Google Photos
< Feedback on Google Photos without slide transition
It's not perfect though -- there is odd-looking stretching animation when switching between landscape and portrait photos, or vice versa; this may also affect neighbour photo (e.g., landscape - (bad) - portrait - (also bad) - portrait - (good, no animation) - portrait ... )
Exactly what I was looking for and works like a charm, thanks!