No this is not Episerver. I'm not familiar with iOS or Android development but I believe for iOS you can register intent, like this https://developer.apple.com/documentation/sirikit/resolving_and_handling_intents/handling_an_intent
if your app is installed it can be selected to open links from specific domains
Generally, you can register your client's domains for the app. There are two parts (see this documentation page):
apple-app-site-associationin the web solution, in which you match the app bundle ID and set up path rules for opening.
Then iOS will open the shared link in the app (if it is installed) or web browser (if it is not installed). Of course, the app need to know how to load the content from the URL. But that is a different story.
Also, if the receiver opens the link on a non-iOS device, the link is always opened in a web browser.
I have a EpiServer website with my client. They also have an app which is outside of EpiServer. My site also has Content Delivery API installed.
The app consumes some pages data using Content Delivery API.
The ask is whenever the users share a content link through the app to other users and if user tries to open the link, we need to check if they have the app installed then open the content in the app else open in browser. I am not sure if there will be any changes or configurations required in EpiServer to achieve this.