so I did not realize I was lacking this until I couldn’t use Twitter or Facebook to login to certain other accounts. I can’t seem to locate the area in Settings where I once had Twitter and Facebook listed (separately from the rest of the apps) and could manage my accounts for those two services from there. I’ve been prompted to “go to settings” and log in multiple times. Does anyone know where these are located now, whether they have been wholly removed, or wherever I need to do something to restore them? Thanks.
Apple has removed these logins for Twitter and Facebook. From https://www.axios.com/apple-removes-facebook-and-twitter-integration-from-ios-11-2433996734.html:
The bottom line: Now Facebook and Twitter will be treated like other apps, with the social networks forced to rely on the same iOS sharing extensions used by all those with whom they compete.
Apps relying on this central login logic need to provide an update for iOS11.