The "please let me know" <https://www.dedp.online/appendix/feedback> link at the bottom of the page gives an ugly Apache 404
heh, I would send feedback about that but ...
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update: so, it seems the Feedback in the sidebar <https://www.dedp.online/appendix/feedback.html> works so it was just a missing page extension. While reading that I discovered the GitHub repo for the project is private, which explains why I couldn't find it, either