Is there a way to use DDNS when PPP is on modem?

[vrapp]

My DSL model kept hanging up, so I decided to try PPP on modem, rather than on the router (maybe it's completely hopeless step, but who knows).

But once router has got private IP address, DDNS no longer works. So I wonder, is there a way to tell DDNS provider the public IP? or perhaps there's DDNS provider who determines my IP by itself rather than expects me to tell?

 

[MarvMart]

I run the DDNS Client on my AC66-U without any problems, BUT I also run the no-ip client on my Media Server which is up 24x7, this combination seems to work for me.
Is it possible that something is perhaps blocking the DDNS requests on the modem?
The no-ip client uses Ports 80 / 443 as well as Port 8245 (which was news to me)