I realize there might be an issue with your app but this is how you get the ringtone.
1st pic is the result of tapping "More" at the bottom of the Edit Contacts screen.
2nd is when you tap "Allow Storage permission"
3rd is what's offered as a sound picker
4th is the sound directory.
Galaxy S21 Ultra 512g(VZW), Galaxy Book (original, VZW), Tab S4, Galaxy Watch3 (VZW)