I don’t fullly understand your current situaution, are you running discourse behind proxy? if yes then probably you just need to expose port 80 and let your proxy server handle https/ssl.
Does that mean you deploying discourse on private cloud/on premise? If the answer is yes, then one common issue, is trying to access the site on LAN vs WAN, if this your cause and accesing the site from other network seems fine i.e. just try to access the site your mobile network then check this ref .
How is it set up, by discourse? If not by discourse then probably you only need to expose port 80.
Hummm, If I understand correctly, the 192.168.1.XXX is your private IP address in LAN, and you probably have a public IP address, which your ISP gives you. So just to be clear in your DNS record you should have your public IP address set to point to your subdomain, not your private ip address (in LAN), and secondaly your router might need to be configured to allow incoming traffic route it, to your private IP 192.168.1.XXX. And your ISP should allow incoming traffic
Alternative you can just tunnel your local traffic to a remote server so that you don’t need to mess with your router setting or think if your ISP allows incoming traffic.
So what is your case, tunnel traffic, or allowing incoming traffic via NAT or DMZ?