The src/Makefile.am states: manualdir = $(prefix)/man/man1 manual_DATA = \ xfce4-sensors.1 This is twice wrong. Firstly, the path misses 'share' directory where manuals are installed. Secondly, autoconf already provides $(mandir) for that. So by forcing a custom path you're disabling the possible user override.
A local expert suggests using: man_MANS = xfce4-sensors.1 This should both use the correct directory, but also figure the 'man1' subdirectory as appropriate on its own. Alternatively, you may prefer to force man1 explicitly: man1_MANS = xfce4-sensors.1 https://www.gnu.org/software/automake/manual/html_node/Man-Pages.html
Thanks, will fix that. I wonder which template I used? Fixed with commit 8e3c0bd