My attempt to explain could be wrong, as your question is broad and a bit unclear. You may give an example of what you want to achieve.
What I am getting at is an app that is a html based but isn't a web page it's an web based
There is a difference between a native app and a web app. A native app is downloaded from the Apple Store or similar and is a real application. A web application is a web site that acts like an app.
Choosing a native app, you have to create and upload at least 2 applications. One for iOS and one for Android. And you have to Notarize the application (send your app to Apple for approval). I think it must be something similar using Android. And you have to pay a share of your profit to Apple. A native app does not use subdomains
Choosing a web app is way simpler, but you have some limitations (reaching camera etc). It is a normal website with some extra stuff added. (manifest etc). You can use subdomains with web apps
I hope I understood your question correctly...