akka-http web-app fails to start on minimal docker jre 11 (what java modules for scala12 akka-http)?

You need to add a jvm argument to your ENTRYPOINT clause:

--add-exports=jdk.unsupported/sun.misc=ALL-UNNAMED

and should look like the following:

ENTRYPOINT ["java", "--add-exports=jdk.unsupported/sun.misc=ALL-UNNAMED", "-jar","/app.jar"]

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