iOS 14 custom alert tone

Yes, I would like to believe that 3rd party apps are excluded for accessing "personal user content" in the iOS system. It can also easily be WhatsApp and Telegram who choose that you can only use Apple standard tones in their apps.

You should be able to use m4r. files, such as alarm sound in the Clock app. I myself have a custom alarm tone and it is in m4r format, loaded into ringtones and I can select it in the Clock app.

Please note that costume ringtones are not between the ringtones you can select in connection with the Bedtime, Sleep/Wake Up function.

I can see you have loaded In The Air Tonight and The Big Bang Theory Theme Song, you can also use them as Alert, Text, AirDrop etc tone.

All "custom tones" will be found along with the ringtones, whether it is a short text tone, or long ringtone. So if I look at those screenshots, then everything looks right. Just load your favorite Alert Tone as if it were a ringtone. It can be found in the Ringtone category, but you can easily select it as Alert Tone.