I’m not sure if this works on PC/Mac, but you can click on the leaderboard icon on locked levels on mobile. It isn’t physically there, however tapping on the location where it would be brings you to the leaderboard. I’m not sure if it’s intended to be there or not, but I’d just like to bring this up.
Hah, whoops! I remember finding that a few months back, but I thought we’d fixed it. Thanks for reporting it, I’ll chuck it on the backlog so we don’t forget again.