Prior to Catalina, one possibility for retrieving on-device logs for an app was to write to a file in a particular location, with the "Application supports iTunes file sharing" plist key set to true.
(see Logging data on device and retrieving the log for examples)
Prior macos 10.15 Catalina, the user would plug in their phone, open iTunes, and find the app and download the files through iTunes directly.
How do I access the files I could previously retrieve through iTunes sharing?