Dear Maintainer, The mandoc(1) man page says: The file /usr/share/misc/mandoc.css documents style-sheet classes available for customising output. However this file is not installed on Debian.
The installation of mandoc.css happens in the cgi-install target: https://sources.debian.org/src/mdocml/1.14.5-1/Makefile/#L448 …but the cgi-install target is not called by the package Debian build files. See e.g. build log https://buildd.debian.org/status/fetch.php?pkg=mdocml&arch=amd64&ver=1.14.5-1&stamp=1613511718&raw=0