Finally got a chance to play around with @khaost's ExtensionKit sample project. Runs straight outta the box on iPad! Unfortunately not on Mac Catalyst (seems to need an entitlement?)

TL;DR, however — you can now build and use plugins in your iOS apps (🥳). Split your app up into separate, tightly-restricted sandboxes to process user-generated content or do anything potentially crashy that you don't want bringing down your app. And they can be shared between apps, too

https://github.com/KhaosT/UIExtensionExample