Here you go. :)

Did you activate user management (acess using a login and a pasword) ?
Because if you did, you have to explicitely authorize each user for each folder you share.

If not, I have no idea what's happening.

Doc updated

Thanks for having shared.

There is nothing in Ubooquity's design that prevents the use of FQDN.
I created a no-ip.com account to test it today, and it worked (I pointed something like myname.ddns.net to my IP address and accessed it using myname.ddns.net:2202).

I don't know why it is not working on your side.