I am not unsympathetic to the concerns you raise about GitHub CloudFlare discrimination, etc., but I am not going to do anything about it in the packaging of qpdf. The qpdf-doc package contains a fully offline version of the manual in HTML and PDF format, which you can read without going to readthedocs.io or github.com. I will include mention of the qpdf-doc package in the manual page for the debian package because I agree that that's a good idea. Regarding your comment that the qpdf-doc package is essential, the reason the doc package is separated as that a minimal distribution doesn't require docs. If you are, for example, building a container image that uses the qpdf CLI, you would not want to include the docs in the container. qpdf works correctly without the doc package installed, so it is not essential.
Hopefully the 12.4.0 package I intend to upload momentarily will at least address the fact that the manual page is silent on the qpdf-doc package's existence. As for the rest, we'll have to pick our battles, and I'm not planning on moving away from github.com and readthedocs.io or changing things that benefit the majority of users.
