Is there a simplest way to make ringtones on Apple Music?

As long as it’s an actual purchased song you have in Apple Music and not one you stream or saved to your device because you have the the subscription you can use Garage Band app on your device.

Scroll down to “How to make a ringtone with GarageBand for iPhone“ in the following link.

https://www.macworld.com/article/616018/how-to-custom-ringtone-iphone.html

I just made a few last night using the method