java -cp "forge-installer-headless-1.0.1.jar;forge-1.15.2-31.1.0-installer.jar" me.xfl03.HeadlessInstaller -installClient %appdata%/.minecraft ...
Running the installer, I got the following error: user@mc-server ~/arcserver [SIGINT]> java -jar arclight-forge-1.19.2-1.0.4.jar Downloading missing libraries ... Downloading mc version manifest ...
You can install Minecraft Forge for free from the Forge website, and then use it to download and enable mods.