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

How can I create and upload a custom iPhone ringtone using MacOS 10.15 Catalina? I have tried to follow the advice given for [uploading ringtones applicable to older versions of MacOS, where iTunes was available](https://apple.stackexchange.com/a/1885/193685) , substituting the replacement **Music** program instead, but I don't seem to be able to drag or open the .m4r file that I have created into Music, nor drag it onto my iPhone in the Finder. Is there still some way to convert other audio files into ringtones and upload them to iPhones when using MacOS 10.15 Catalina?