See this description:
https://frappeframework.com/docs/user/en/guides/data/using-data-migration-tool
It’s been ripped out from ERPNext (or Frappeframework?).
Where did it go? And why? It looks so useful!
Where can I find the last (or best) version of this tool, to build on?
Or is there some replacement with similar functionality?
I think it is on version 12.
Why was it removed? It was hard to maintain and had too many bugs, so it was deprecated after version 12.
It (or parts of it) can be found, for instance, here:
or
or in other similar places of the older versions.
The docs page I mentioned in my post above says “Data Migration Tool was introduced in Frappe Framework version 9.”, so other versions might have relevant code, for learning, reuse, resurrection, improvement, dev-tool-building, etc.
The framework having improved, libraries like virtual doctypes might help explore/build/adapt connectors for data migrations.
What about the upcoming Frappe Studio, will it include functionalities for building data migration connectors, integrations and such?