What you're looking for is called a histogram and you're presupposing that it will be a bell curve (although you're certainly correct)
Well I Lichess doesn't do this directly, so I created a python snippet to do it.https://gist.github.com/MarkDunne/c0f89988837b9f8de9f1
The little program uses lichess' API to first fetch a list of users then queries the ratings for each user. Because of the way the API is structured and the fact that the servers don't like getting too many queries too fast, the program works slowly through the list of users (sleeping for 1 second between each user).
Someone with some free time to spare can run the program for a large number of users and generate the plots that you want