This is actually a display issue or a bad UI design. On the File Sharing page it prompts you to set up DDNS, but it's already set up and it's actually working via the domain name.

The blurred text on the first screenshot is my public IP and I can't select/choose the domain in any way.

Hello everyone, I'm trying to set up an "Internet FTP", but for some reason the DDNS info doesn't update/doesn't work. The settings under USB > Storage Settings keep prompting me to set up DDNS: But...