Question to the devs: is it the case that the Notion API does not offer good access to the Page Contents or that the Page Contents data it provides is hard to work with (e.g. proprietary blocks)?
I ask because I recently realized I might be able to work around the Fibery limitation by using Zapier or Integromat to connect between Notion and Fibery. But attempts with both of them did not show any Page Contents that was accessible in the content that got pulled from Notion. Their API documentation does seem to indicate page contents is available, but it appears to be in a proprietary JSON format (the more I read/research for writing this reply, the more I may be answering my own question 
).
Perhaps this could be used to ingest:
But it gets back to the issue for me of not being able to code my own bulk MD importer for Fibery. 
Ironically my use of Notion is partly just a hoped-for workaround to the lack of Easy import of markdown docs to wiki. I could do it via CSV, but I haven’t found an easy, non-programmer way to get Markdown into CSVs! 