I am wondering if it is possible (and if so, some elaboration and steps to achieve) building out a custom iMessage Extension WITHOUT using storyboards? I have my core app, and then have the additional iMessage extension target. My main app is working fine without storyboards.
I followed the tutorial here, however it is not working and makes the original app look really funky upon deleting the Launch screen interface file base name info.plist entry from the main app. This tutorial is from 2016 and uses Objective C, so that might also have something to do with it.
I know that the launch screen for the main app now requires a storyboard, and everything is working fine there.
One way is to do it in SwiftUI.
Here's a link to another question that has a complete example of a bug, but to your question has a stub of a message extension that displays a very simple view. You could expand on that.
imessage extension app group conversation send fails on first run