https://remarkup2wikitext.toolforge.org/
Uses a regex soup, and needs manual oversight, but works well enough to be useful as a timesaver and there doesn't seem to be any other remarkup-to-anything library available. (To give an idea, this was the amount of manual fixup required after exporting the 15 frontend tasks.)
The current code is horrible so it needs some packaging + documentation before it can be published.
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