I used to have some iOS apps that were authorized to access my Twitter account through the legacy Twitter integration feature in old iOS version. This feature is no longer available in iOS 11.
According to Twitter (https://help.twitter.com/en/using-twitter/revoke-twitter-access-on-ios-app) :
Note: Though you will see other specific apps like Twitter for iPhone or Camera for iOS listed in your active connections, you cannot revoke access to these individual apps; you have to revoke access for the entire iOS integration.
How do I revoke those apps' access if all my devices are running iOS 11?