Where to find the leaderboards for all rides in the app?

Not sure if I understood you correctly, but you can find the results of yourself and others if you click on a movie and open up the tab "Opponents"
Under Opponents you find another selection "All", "Myself" and "Following"
I've noticed loading opponents sometimes is buggy. It does not always load the names at the first attempt. It loads for me when I go back and forth between tabs.

Note that these result "reset" when a newer version of the movie is published in Beta (like v1>v2 and so on..)

Example:

Due to much of Beta ride history/Data being lost several months ago when developers updated the server and lost all history {supposedly was backup} but not re-instated and also when an update to film is released by Phil then previous opponent data/history of the ride disappears, so in beta it isn`t too reliable a feature... if wish to ride opponents regularly install the retail version where records of ride data stays as the video isn`t replaced/updated..

Great, thanks. Found it, that was what I was lookng for, thanks for helping me out!