Hi,
if anyone would be able to give a hint what might be wrong so that the following error triggers when trying to make the manual, any idea/hint really would be highly appreciated:
[ 96%] Built target target_media_images
[ 96%] Checking validity of the usermanual darktable.xml
[ 96%] Built target validate_usermanual_xml
[ 96%] Generating the profiled docbook xml file
I/O error : Attempt to load network entity http://docbook.sourceforge.net/release/xsl/current/profiling/profile.xsl
warning: failed to load external entity “http://docbook.sourceforge.net/release/xsl/current/profiling/profile.xsl”
compilation error: file xsl/darktable_profile.xsl line 3 element import
xsl:import : unable to load http://docbook.sourceforge.net/release/xsl/current/profiling/profile.xsl
make[3]: *** [doc/usermanual/CMakeFiles/darktable_single_xml.dir/build.make:397: doc/usermanual/darktable_profile.xml] Fehler 5
make[2]: *** [CMakeFiles/Makefile2:6826: doc/usermanual/CMakeFiles/darktable_single_xml.dir/all] Fehler 2
make[1]: *** [CMakeFiles/Makefile2:6693: doc/usermanual/CMakeFiles/darktable-usermanual.dir/rule] Fehler 2
make: *** [Makefile:2747: darktable-usermanual] Fehler 2
I have no idea whats going on here as I still am more or less a user rather than programmer… Before my reinstall to Ubuntu 20.04 all was smooth 
Hints really would be appreciated.
Thank you so much.
Cheers, Martin