As Apple is forced to allow sideloading iOS apps, there is one thing going to happen: for "some reason" all Meta company apps are distributed as sideloading. Mark my words.
Sure Meta will also distribute apps in App Store but quickly ask user to "upgrade" from sideloading source.
What iOS developers can do? Start flooding the market with very nasty sideloaded apps which purpose is to end up in news and cause global awarness to how bad idea sideloading is.