I assuming: you have a server that is used by multuple domains or sub domains all pointing to the same server.
So mainly you need to run a main proxy server which would listen to ports 80 and 443 if you run TLS/SSL.
The main proxy server would then route the traffic based on the host/domain, i.e. discourse.example.com => go to discoures, blog.example.com => go to wordpress.
I think you have multiple option how to handle such deployament, because typically wordpress come shipped with its own proxy server, as well as discourse. So your option could be:
- Use discourse nginx proxy server as the main one and it would proxy to wordpress
- Use wordpress as the main proxy server and it would proxy to discourse
- Use your own main proxy server that it would be proxy to both.
In any case whatever you choose, I think the TLS/SSL usually would be handled by the main proxy server.
I have used discouse in the the first two secinaro above, when I used other proxy server to handle incoming traffic (first option) I had to change ports, and turned off TLS and instead let the other proxy server handle it. And for the second secinaro, I changed nginx conf file inside the discourse contianer and add a declarative for another server and then generated certificate for it using certbot.