Is there a list of approximate ELO ratings for each Stockfish level? I want to create something that will select an appropriate Stockfish difficulty setting automatically given the player's rating. The straight Stockfish v11 that I've downloaded has 20 difficulty settings, and various other settings for controlling thinking time. Is there a resource that has approximate ratings for the levels? If that doesn't exist, what method would be recommended for finding the approximate ratings of chess engines when I'm starting from scratch?
EDIT: Sopel gave a link some time ago, that answers the problem, although they did it in comment form so I can't mark it as the correct answer
They have a development pipeline doing testing based on one of the early versions.
I saw a graph of such test in some heavy loading page from Next Chess Move website:


Stockfish Development Builds


The development page gathering the test linked from the Fishtest wiki:


Stockfish Testing Queue


And for completion:


Fishtest GitHub Repository Wiki