Several web servers can be connected to one internal network.
Several web servers can be connected to one internal network.
Your setup involves multiple services running locally and needing external access. You're using a Raspberry Pi with a webserver and Minecraft hosted internally, while also aiming to expose it via mc.mydomain.com and panel.mydomain.com. To achieve this, you'll need to configure port forwarding on your router for each service. For the NGINX panel, ensure it's installed on the old PC and accessible through the same internal network. Consider using a reverse proxy or load balancer if needed.
Only need to forward the port used by Minecraft (25565/tcp) to the old PC. For the web server, you might keep it on the Pi and run the management page on another port (for example 88 and 488). If you prefer not to have the page on a different port, you could relocate the web server from the Pi to the old PC or install a proxy on the Pi. Web servers can recognize the domain being accessed to alter what is shown in the browser. They are commonly referred to as virtual hosts; you can find details for Nginx here.