CoD4 is a Windows application, that is true, but it has dedicated server for linux as well, which is supported too.
It does not complicate things, probably easier, you just need to get familiar with it, it’s not that hard.
Yes, you can use whatever linux you want on Proxmox, and yes, it is possible to use the VM like that.
You need to make sure you have proper Public IPv4 address on your home network, and you are not behind CGNAT.
Second you need to enable port forward in your router to your VM to be able to be reachable from outside LAN.
There are tutorials how to setup this properly, at least the Linux Dedicated server part, the home network and Proxmox setup I can guide if you have questions, you just give it a static IPv4 address on your network, leave IPv6 as is, and you should be okay there too.
I would not use a full VM for this, just a Debian/Ubuntu container, more lightweight, for this application it’s more than enough.
I use Ubuntu 24.04 containers across my homelab, I would suggest you do the same.
You will come across some hurdles if you not familiar with Linux, but I can assume if you use Proxmox, you have somewhat of a Linux knowledge, at least a base level.
If you have questions, probably easier to hop on to Discord, we are more than welcome to assist there, probably quicker too.
Here are the guide you need to follow.
