http://r53zi7kxyqd72fuvhztzi25fo2bze7fqjefze7k6t6kiq74pzaq5suyd.onion/posts/2020/2020-07-27.html
I hope you find this guide as useful as I do. Have fun. The source for this guide is this topic from osu! forums. Edit: I did a mistake and mentioned that there's a Mac version for osu! on the developer's site for the game. Unfortunately, there's only a page on Tumblr that has information about how to install osu!