Which port are you trying to get to your Homeassistant , you should be using https://XXXX.duckdns.org:8123 you shouldn’t need to to port forward 443 if you are not using a reverse proxy.
If your ISP use Carrier Grade NAT, then your ISP needs to make a portforward too, because you are behind two NATs then and you only control one of them.
sorry if i’m not correctly, but it basically means that my router ip is different from my public ip ? i read something like that here in the community but i don’t know if what i’m saying is correctly.