iOS app with subscription on remote server
Yes this is allowed. However you are required to let users sign up through the iOS app. You get 85% and Apple gets 15%.

3.1.3 Content-based “Reader” Apps
Apps may allow a user to access previously purchased content or content subscriptions (specifically:
magazines, newspapers, books, audio, music, video, access to
professional databases, VoIP, cloud storage, and approved services
such as educational apps that manage student grades and schedules),
provided the app does not direct users to a purchasing mechanism other
than IAP.
3.1.4 Content Codes
Apps may not use their own mechanisms to unlock content or functionality, such as license keys, augmented reality markers, QR codes, etc. In limited circumstances, such as when features are dependent upon specific hardware to function, the app may unlock that functionality without using in-app purchase (e.g. an astronomy app that adds features when synced with a telescope).

Source: https://developer.apple.com/app-store/review/guidelines/#content-based-reader-apps