A Mallard set under $XDG_DATA_HOME/help is one Yelp cannot draw the figures
of: its sandbox exposes the system help directories but not the user's data
directory, and each figure is a separate file the page references. The pages
open without their images, and through the app's help: URI the viewer spins
for ever because the failed image fetch means the page's load event never
fires -- which reads as a navigation failure, not a missing resource.
The alert and the manual both recommended install-help-user as the no-root
route, so they led users into exactly that case. Name the system-wide install
first and state the user-local caveat where the advice is given, and record
the finding in the GTK traps invariant so the next figure that will not draw
is not chased as a markup or a file problem.