Maybe not side projects, but I'm running Android and Kde Connect, Home Assistant, Element or Mastodon are all listed as having more than 1 million install. I can't imagine these FOSS projects paying any significant amount of money just to distribute their free apps.
OsmAnd has more than 10 million installs, VLC more than 100 million. Can you imagine the fees? They obviously don't have hundreds of thousands of dollars on hand to pay every month to Apple.