How to add ringtones not purchased from Apple onto iPhone?

On my earlier iPhones, I was able to load self-made ringtones. These included mainly snipets of songs

Apple didn't have in it's library, songs my brothers wrote and played in their band, and some melodies I pieced together. I could use sections of songs that had meaning, not just choruses or the first 60 seconds. I could do this from my Windows computer through iTunes. I haven't had to change my ringtones since I traded in my iPhone 6 for the iPhone 11. It's been about 5-6 years. Since I purchased the iPhone 16 Pro I find that most of those tones disappeared from the list, and I can't find a way to add non-Apple purchased ringtones to the phone. Does anyone know of a way to put custom ringtones on the iPhone anymore?