Additionally, Linux hosting is possible but not encouraged for IW6 and S1, as it hasn’t been tested recently by me, the sole developer of these clients.
It adds a layer of complexity that I do not want to maintain for these clients, so proceed at your own risk.
Here is the guide written for IW4x Linux: IW4x Server Install Guide Linux.
You can also use Pterodactyl eggs for IW6 and S1, which might make the process easier for you: Pterodactyl Eggs for IW6 and S1.