Installing Mosaic on Plone 6: Cannot find a field for the record plone.lessvariables

I tried installing Mosaic on a brand new Plone Classic 6.0.0b2 and I'm getting the following error:
(I did pin "" due to this known issue -> Plone 6 Classic with Mosaic - No module named '')

Traceback (innermost last):
  Module ZPublisher.WSGIPublisher, line 167, in transaction_pubevents
  Module ZPublisher.WSGIPublisher, line 376, in publish_module
  Module ZPublisher.WSGIPublisher, line 271, in publish
  Module ZPublisher.mapply, line 85, in mapply
  Module ZPublisher.WSGIPublisher, line 68, in call_object
  Module Products.CMFPlone.controlpanel.browser.quickinstaller, line 544, in __call__
  Module Products.CMFPlone.controlpanel.browser.quickinstaller, line 320, in install_product
  Module Products.GenericSetup.tool, line 399, in runAllImportStepsFromProfile
   - __traceback_info__:
  Module Products.GenericSetup.tool, line 1511, in _runImportStepsFromContext
  Module Products.GenericSetup.tool, line 1323, in _doRunImportStep
   - __traceback_info__:
  Module, line 80, in importRegistry
   - __traceback_info__: registry.xml
  Module, line 125, in importDocument
  Module, line 264, in importRecord
   - __traceback_info__: record name: plone.lessvariables
ValueError: Cannot find a field for the record plone.lessvariables. Add a <field /> element or reference an interface and field name.

I figure this has to do with things that are no longer in registry.xml

After manually going to Site Setup > Configuration Registry > Add New Record and adding a record called "plone.lessvariables" of type "Text", Mosaic installed successfully. :man_shrugging:

Interestingly... after installation plone.lessvariables remains blank.

lessvariables is outdated in Plone 6 and the latest Mosaic 3.0.0a6 doesn't use it anymore ... check the latest versionpins for Plone 6 here

Thanks @petschki the `versions-ecosystem.cfg' will be very helpful.