Pro-Tipp: forget Archetypes as of today.
Perform a proper export of your data e.g. using collective.jsonify and use e.g. transmogrifier for a proper import into Dexterity content-types.
We migrated a bunch of sites (including partial content) with a script that runs against the old Plone site and inserts the data as new content over plone.restapi.
Everthing else sounds like broken-by-design nowadays.