I am testing / updating some add-ons to Plone 6.
A lot has problems with 'registry.xml', but the fixes seems rather simple.
For example collective.collectionfilter will work if I change
<records interface="Products.CMFPlone.interfaces.IResourceRegistry"
prefix="plone.resources/collectionfilter-bundle"
to
<records interface="plone.base.interfaces.resources.IBundleRegistry" prefix="plone.resources/collectionfilter-bundle">
<value key="enabled">True</value>
<value key="jscompilation">++plone++collectionfilter/collectionfilter-remote.min.js</value>
<value key="csscompilation">++plone++collectionfilter/collectionfilter.min.css</value>
<value key="expression" />
<value key="depends" />
<value key="load_async">False</value>
<value key="load_defer">False</value>
Is there some docs /suggestions on 'which bundles to change' ?