Unfortunately that's also the primary reason Kotatsu was targeted and shutdown
Bundling the sources with the app has become very risky because one specific multi-billion dollar Korean company (Kakao) has openly made it their mission to hunt down these apps' creators and nobody can stop them. They literally brag on Twitter about it and everything.
So the best way to avoid litigation and ensure longevity at the moment is to completely separate the app/reader from the actual sources of content.
But it's not that inconvenient. Once you add the repository url you can see all the available extensions in-app and download the ones you want. They are also updated automatically so it's not that involved after the initial setup.
All Mihon forks also have an update checker so you'll pretty easily keep the main app updated as well.