Universal Links let you connect to content deep inside your app using standard HTTP or HTTPS links.
Universal links cannot be opened from within an app that supports them. iOS believes you want to exit the app and redirects users to Safari.
The best solution here is to:
Use a classic scheme based URL (such as "myapp://mydeeplink")
Or use a deeplink delegate to manually redirect the user from the delegate method. You will find more information on that point in the documentation.