JavaFX ignores HiDPI scaling settings on Ubuntu 20.04

ADDITIONAL SYSTEM INFORMATION :
OS:
Ubuntu 20.04.1 LTS

JAVA:
openjdk version "11.0.9" 2020-10-20
OpenJDK Runtime Environment GraalVM CE 20.3.0 (build 11.0.9+10-jvmci-20.3-b06)
OpenJDK 64-Bit Server VM GraalVM CE 20.3.0 (build 11.0.9+10-jvmci-20.3-b06, mixed mode, sharing)

A DESCRIPTION OF THE PROBLEM :
Running a JavaFX application on Ubuntu 20.04.1 LTS does not scale as expected. The font and other controls are tiny on a 3840 x 2160 screen with a scale factor of 200%. The same application works well on Windows 10 with the same scale settings of 200%.

The example for Ubuntu 20 show that it is not working correctly. You can see that the factor is always 1.0 no matter what is set in the Ubuntu environment.

REGRESSION : Last worked in version 15.0.1

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Build the project and run it.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The UI is scaled by a factor of 2.0 (200%) and this is also shown in the label text.
ACTUAL -
The UI is NOT scaled and the label shows a factor of 1.0 (100%)

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https://github.com/javafxports/openjdk-jfx/files/5683083/HelloFXML.zip

(See https://github.com/javafxports/openjdk-jfx/issues/643 for some additional console output)
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FREQUENCY : always