When using the iOS app, tapping the rank numbers on the Dashboard > Stats (having enabled "Show my ranking compared to other users for various stats"*) shows a "Click to see users near your rank." tooltip. Unfortunately, no amount of tapping actually shows the ranking list.
When using Safari's Add to Home Screen PWA, tapping a rank number (just once) shows that tooltip very briefly before closing it and showing the ranking list. It also seems that the ranking user list popovers stack infinitely rather than replace each other, so if you tap/click on multiple rank numbers (or even on the same number a bunch of times), you can end up with a number of those popovers to dismiss if you'd like to view the page below them.
* This setting is a bit out of the way; perhaps including similar functionality on Community > Leaderboard would make it a bit easier to find.
Sorry for the delay - if you could get a video of this happening, it would help a ton with me getting it fixed. If you cannot attach it to this forum thread, you can email me the link or the video itself at michael@renshuu.org