Https problem and casting dashbord to Google nest hub

Im new to Home Assistans.
Im running HA on a computer with Debian 11 (no GUI).

I have created a “Duckdns domain” and “lets encrypt”.
Those seems to work.
Why i want those 2 are that i want to cast desbord to my Google Nest Hub (gen 1).
When i cast it recive it but it cant show any dashbord and i get an error saying “Not Connected. ERROR: Unable to connect to the Home Assistant websocket API”.
Where should i start looking?

Then i cant connect to Home Assistant with https. Could those two problems be connected somehow?

Note: It could be easier to just have the Home Assistant Cloud service. But i dont want to have subscription solution. At the moment i dont have a single subscription regarding my Smart Home.
I was paying for IFTTT but i canceled it cause i found Home Assistant.

Start by confirming that the Google hub supports websockets