get "ClassNotFoundException: org.apache.sling.launchpad.app.Main" when trying to run aem-author-p4502.jar on ubuntu.

I got a quickstart.jar and license key for development from Adobe.

i renamed it to aem-author-4502.jar and if I double click on it on my windows laptop, it works.

My laptop is not strong enough to run AEM as well as my dev tools, so I am trying to run it instead on my dev linux box.

Its ubuntu 20.04 LTS.

I installed the oracle version of java 11:

aem@author1:~/author$ java -version
java version "11.0.9" 2020-10-20 LTS
Java(TM) SE Runtime Environment 18.9 (build 11.0.9+7-LTS)
Java HotSpot(TM) 64-Bit Server VM 18.9 (build 11.0.9+7-LTS, mixed mode)

JAVA_HOME is set to /usr/lib/jvm/jdk-11.0.9/

the box has 2 CPU and 4GB ram, and 32GB SSD free.  It has nothing else running and is headless.

If I try to start the jar thusly:

aem@author1:~/author$ java -jar -XX:MaxPermSize=256m -Xmx1024M aem-author-p4502.jar

Then I look in the stderr log file I see:

Low-memory action set to fork
Using 64bit VM settings, min.heap=1024MB, min permgen=256MB, default fork arguments=[-Xmx1024m, -XX:MaxPermSize=256m]
The JVM reports a heap size of 1024 MB, meets our expectation of 1024 MB +/- 20
Setting properties from filename '/home/aem/author/aem-author-p4502.jar'
Option '-quickstart.server.port' set to '4502' from filename aem-author-p4502.jar
Verbose option not active, closing stdin and redirecting stdout and stderr
Redirecting stdout to /home/aem/author/crx-quickstart/logs/stdout.log
Redirecting stderr to /home/aem/author/crx-quickstart/logs/stderr.log
ResourceProvider paths=[/gui, /gui/default]
java.lang.ClassNotFoundException: org.apache.sling.launchpad.app.Main
at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:471)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:588)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
at java.base/java.lang.Class.forName0(Native Method)
at java.base/java.lang.Class.forName(Class.java:398)
at com.adobe.granite.quickstart.base.impl.exec.Bootstrap.run(Bootstrap.java:83)
at com.adobe.granite.quickstart.base.impl.Quickstart.run(Quickstart.java:273)
at com.adobe.granite.quickstart.base.impl.Main.<init>(Main.java:919)
at com.adobe.granite.quickstart.base.impl.Main.main(Main.java:981)
Quickstart: aborting
MAIN process: shutdown hook
MAIN process: exiting

Any ideas?

Here I am assuming I dont need to start the jar as root, that it will run as a user (as its not trying to use port 80 or similar)

What else I tried:

1. naming the jar file cq-author-p4502.jar  as some articles say it should have this name. Same error.
2. running start script:
   1. chmod u+x /crx-quickstart/bin/*
   2. cd crx-quickstart/bin
   3. ./start
   4. This instantly terminates with no message or error, and no java process running.
3.