I have installed Discourse on an Ubuntu server. I have a domain name with “google domains” that uses dynamic DNS to point to my server. I can hit my server remotely using the domain name from outside my network and can access other apps on the server. However, I cannot access discourse outside my network using the domain name (I have port forwarded all the appropriate ports).
When connected to my home network my discourse installation works as it should when using the domain name despite going through the dynamic DNS.