I have tried to copy a ringtone to the usr/share/sounds/ubuntu/ringtones/ folder, but it will not copy. Is it RO? if so is there a way to change permissions for this folder only [there is information to change it for the whole phone]?
The root filesystem is read-only and you have to remount it in read-write mode with this command
sudo mount -o remount, rw /
and copy the ringtone afterwards.
After that you can restart the phone and the root filesystem will be read-only again.