When you enter “Settings” in the “Device”-section you will find “Sound & notification”.
There you can select/change the "Phone ringtone"
Selecting this option, you should be asked:
“Complete action using Amaze” having the options “Just once” and “Always”.
Amaze is a filemanger, that allows to choose where the ringtone is stored.
In the top-left corner you find a symbol, that will open a menu (from the left), where the SD-card is available (a combination of letters and numbers like “AE9B-2AE3”).
Selecting this option takes you to the file system of your SD-card and you can navigate to your ringtone directory.
Btw. your question gives the same directories for the system ringtones and your private ones.
Thanks for that.
I had to install Amaze because I removed it as it was crashing all the time.
It now is possible to use other ringtones . . . but it should be done from the Media Storage App - but that’s just my opinion.