samples VS jpackage-maven-plugin

If you're relatively new to this, I would recommend checking out the JavaFX documentation at https://openjfx.io/openjfx-docs/#maven and starting from the samples: https://github.com/openjfx/samples/tree/master/HelloFX/Maven

i also replaced the build.gradle file contents with what the openJFX suggested i changed it to. then i sync'd it after changing the javafx version in that .gradle file to 17.0.1 instead of 16.

An example pom file (maven) for a JavaFX program looks like https://github.com/openjfx/samples/blob/master/HelloFX/Maven/hellofx/pom.xml

Yes, JavaFX is a pain to configure. I'd recommend using Maven or Gradle with the JavaFX plugin to manage your application, that way you don't need to download and configure the entire OpenJFX SDK. There are samles for both Maven and Gradle in the repo you linked, so I would try them out. Note that only the Gradle sample includes a wrapper, so if you try the Maven sample you'll need to install Maven first.

Non-modular project (i.e. not using java modules): https://github.com/openjfx/samples/blob/master/CommandLine/Non-modular/Gradle/hellofx/build.gradle

example maven no modular project structure here https://github.com/openjfx/samples/tree/master/IDE/Eclipse/Non-Modular/Maven/hellofx/src/main

I searched for some jpackage plugin for maven. There were some stuff, but no enough examples or documents were found, and seems not maintained frequently.

As above we want to rely on Maven and fortunately, we got a well-packed plugin (JPackage Plugin) on Maven Central that we can add: