The purpose of this guide is to show you how to manually upload a server.jar of a specific version you want onto your server. *Some versions for various reasons aren't included on the built-in version selector.
Your server must be stopped/off.
You have a general understanding of our Game Panel.
You understand you can use File Manager or SFTP.
This example will guide you through installing Forge for Minecraft 1.20.1, specifically Forge version 47.3.12.
Goto the Forge download page
In my case I'm going to the 1.20.1 download page - ttps://files.minecraftforge.net/net/minecraftforge/forge/index_1.20.1.html
Click on "Show All Versions"
Follow the download page and skip any ads as needed
Your web browser should now download the forge installer .jar
If it does not, check your ad blockers or try another browser
Go to your Downloads folder and create a folder called "Forge"