[BeetleB]

Something must have clearly gone wrong with the install (or perhaps there is a minimal install version...?) If this were Gentoo, I would suggest that perhaps the "doc" USE flag was not enabled?

[mindcrime]

Looks like Debian/Ubuntu and derivatives don't install the Emacs manuals by default. I had to do this to get it on my PopOS box:

sudo apt-get -y install emacs-common-non-dfsg