Hi @EclipseWizard !
Thanks for the questions,
You can already find a lot of information on this thread.
Regarding Rust, Ruby and Scala, Sonar will not be including the plug-ins for Rust, Ruby, or Scala in the marketplace. A requirement for plug-ins in the marketplace is that they are actively maintained, and Sonar will not be doing that. They are available for the community to eventually do so. You can still compile them and install them manually in the meantime.
For the Java SE engine, it is going to be extracted once we have it covered fully by our proprietary engine which is getting rolled out progressively to our free SQC tier and our paying tiers of SQC and SQS.