for more than a year, I have set out migrating a Plone 4.2 website into up-to-date versions (Plone 5.2, Python 3), and by now I have a fairly good idea of the whole roadmap.
As a first step, I've upgraded the site to Plone 4.3.19, converting the multilingual content from Linguaplone to plone.app.multilingual. The resulting site has been online for several months, everything fine.
The next step is to convert Archetypes content (only standard types, nothing custom) to Dexterity. If I use some caution, I can go through the whole process (migrate exerything except folders first, then migrate folders). I've tried it both in Plone 4.3.19 and Plone 5.2.3.
Plone 4.3.19: just after migration, Language Root Folders seem to be broken, Plone complains they don't have the iTranslatable interface. I can reinstall the multilingual support, then force Plone to refresh the setup (e.g. by adding a language, then removing it), and then the site will be displayed in both languages (LRFs now work). Only problem, all translations links are lost.
Plone 5.2.3: If I don't reinstall the multilingual support, the multilingual control panel is broken, because of missing registry keys. I can manually reimport them from XML, not sure if it's the right solution. Or I can reinstall the multilingual support, and the result is the same as in Plone 4: LRFs work, but translations are lost.
I am about to embark on writing a custom script to save / restore translation relations (save from reference_catalog into a file, restore from that file), but before I do that, has anyone met the same problem? Am I doing something wrong? I have done a lot of googling for weeks, even months, but have never found any clue.
Thanks in advance, Laurent.