How can I set a custom ringtone on my iPhone without using GarageBand?

Apple has no guidance on how to do this without GarageBand. I've seen a few slightly different tutorials, none of which worked for me. The furthest I was able to get was like this: - Open the audio file (less than 40 seconds) in Apple Music for Mac and convert it to an AAC file. - Rename it from .m4a to .m4r to convert it to a ringtone file. This works for files less than 40 seconds because .m4a and .m4r use the same file format. - Some guides told me to drag the file into the "Tones" section of Apple Music, but this section does not appear for me. Instead, I dragged it from Finder onto my iPhone. - Sync the phone, which successfully added the song to my Apple Music library on my iPhone. - [People have reported](https://apple.stackexchange.com/questions/431183/how-do-i-set-an-m4r-file-ringtone-i-airdropped-to-my-iphone-13) being able to select "Download All Purchased Tones" on their iPhone under Settings > Sounds & Haptics > Ringtone in order to make the file appear as an option. When I selected it, it did nothing except temporarily remove the option to download tones. Most guides suggest using a third-party tool, but I find this strange. If additional software *is* required, why do so many people claim that it isn't? I've been able to set custom ringtones through GarageBand with no issues, but it bugs me that I can't work out how to do it without. If anybody knows what GarageBand is doing under the hood when you make a ringtone, that would also be useful. If anybody has any information or tips they think are relevant, even if it doesn't solve the problem, please provide it. If it helps, I'm using iOS 18.4 and MacOS 11.7