The server installer is asking for X11 ??

[Sigmanificient]

Hi, your server installer ask for XORG variable to be set.

To run on a server? That make no sense
Your not supposed to have xorg on a server.

openjdk version "1.8.0_282"
OpenJDK Runtime Environment (build 1.8.0_282-b08)
OpenJDK 64-Bit Server VM (build 25.282-b08, mixed mode)
:/home/container$ java -Xms128M -Xmx8192M -jar forge-1.12.2-14.23.5.2854-installer.jar
JVM info: Oracle Corporation - 1.8.0_282 - 25.282-b08
java.net.preferIPv4Stack=true
Found java version 1.8.0_282
Exception in thread "main" 
java.awt.HeadlessException: 
No X11 DISPLAY variable was set, but this program performed an operation which requires it.
        at java.awt.GraphicsEnvironment.checkHeadless(GraphicsEnvironment.java:204)
        at java.awt.Window.<init>(Window.java:536)
        at java.awt.Frame.<init>(Frame.java:420)
        at net.minecraftforge.installer.InstallerPanel.run(InstallerPanel.java:408)
        at net.minecraftforge.installer.SimpleInstaller.launchGui(SimpleInstaller.java:170)
        at net.minecraftforge.installer.SimpleInstaller.main(SimpleInstaller.java:143)