Ok. Enabling the tls did not solve the issue 
I managed to enable the tls, and deployed the graylog with the cert and key).
Still getting these “(blocked:mixed-content)” on the browser, when trying to load the UI.
I probably need to configure the https to the nginx, something like Sean is pointing above.
On this post Web interface not working behind Nginx - #4 by jan
there is:
" when you have http s you need to adjust that in the nginx configuration:
proxy_set_header X-Graylog-Server-URL https://$server_name/;
"
I have tried to set it up on helm, like:
–set graylog.ingress.annotations.nginx.ingress.kubernetes.io/proxy_set_header='X-Graylog-Server-URL https://$server_name’ `
Deployment does not fail, but also the https is not working.
Kind a lost here, I guess the enaling the tls is not working because of the nginx, but not totally sure what is needed for nginx