New update-Find my Friends

With iOS 13, Apple introduced the "Find My" app which combined both the Find My Friends and Find My iPhone apps. Any app that relied on these apps may not work ... as you found out. I suggest that you contact the app developer to see if they plan on providing an update that will.

QuestionConcern wrote:

is anyone else's phone saying "this app requires specific features not available on this device" for Find My Friends?

“Find My Friends”?

There is no such application with iOS 13.