Now Publishing is working. Root cause is,
In the Tridion Site 9.1 installation media for the Deployer role there are now 9 deployer folders. The previous Deployer and Deployer-combined folders are now used to run with the add-ons framework. Pipelines are not enabled by default which causes the error.
The quickinstall script or the documentation steps for a ...
Failure to prepare for deployment often indicates a false Content Deployer configuration or problems with customizations.
If your publishing fails in the'Preparing for deployment' phase, try the following:
Is your Content Deployer configuration (deployer-conf.xml) correct?
Are you using a custom Module and/or Processor in your Content Deployer? The code for ...