How to create a custom iPhone ringtone using MacOS 10.15 Catalina?

Solution 1:

'Create ringtone' part for Catalina (and older macos versions as well) is pretty simple and straightforward if you are comfortable with terminal.

MacOs comes with built-in afconvert. For example, to convert mp3 file 'mysound.mp3' to ringtone (.m4r file) mysoundringtone.m4r:

afconvert -f m4af -d aac mysound.mp3 mysoundringtone.m4r

Need to be in same directory with source file or pass path along with filename(s).

'Upload part': one can connect iPhone to computer and drag-and-drop ringtone file to iTunes while it's on iPhone 'General' tab. After that locate newly created ringtone on iPhone in Settings > Sounds & Haptics > Ringtone (above built-in ringtones, separated by line).