Ubuntu/pop os!

use the command line :

sudo apt-get install openjdk-11-jdk

sudo update-alternatives --config java (make sure it's set to java 11

sudo apt-get install openjfx

now edit the beatoraja-config.command it should look like this now :

"#!/bin/bash

export _JAVA_OPTIONS='-Dsun.java2d.opengl=true -Dawt.useSystemAAFontSettings=on -Dswing.aatext=true -Dswing.defaultlaf=com.sun.java.swing.plaf.gtk.GTKLookAndFeel'

cd "$(dirname "$0")"

exec /usr/lib/jvm/java-11-openjdk-amd64/bin/java --module-path /usr/share/openjfx/lib --add-modules=javafx.base,javafx.controls,javafx.fxml,javafx.graphics,javafx.media,javafx.swing,javafx.web -Xms1g -Xmx4g -cp beatoraja.jar:ir/* bms.player.beatoraja.MainLoader"

Save it and now ...

In terminal run 

sh *.command

Make sure to make a new profile for linux since they don't work with profiles used with windows

Disclaimer : This is what I did to run beatoraja on pop os! in 2020. Does it work now? I have no clue.