Running LibreOffice 6.0.7.3 on ubuntu 18.04. I have several fonts which are not available in LibreOffice, but are available in other applications, for example I copied a bunch of fonts from my Windows partition to ~/.fonts. All Calibri fonts are available in Emacs, but not in LibreOffice. Calibri {Regular, Light, Light Italic} available in both Emacs and LO, while Emacs has additionally Calibri Bold. Similarly with Arial: only Arial regular and Arial Black are available in LibreOffice, while Emacs can see much more: Arial {Regular, Black, Bold, Bold Italic, Italic, Black Black, Black Italic, Black Bold Italic}. Some of these are apparently different styles residing in the same ttf files, but some are independent ttf files.
This is a problem, because when modifying large existing powerpoint files, thousands of components use substitute fonts which don’t fit properly on the slides; changing everything by hand would be days of work.
Here are the calibri fonts known on my system:
$ fc-list |grep -i calibri|sort /home/user1/.fonts/calibri.ttf: Calibri:style=Regular /home/user1/.fonts/calibrib.ttf: Calibri:style=Bold /home/user1/.fonts/calibrii.ttf: Calibri:style=Italic /home/user1/.fonts/calibril.ttf: Calibri,Calibri Light:style=Light,Regular /home/user1/.fonts/calibrili.ttf: Calibri,Calibri Light,Calibri Light Italic:style=Light Italic,Italic /home/user1/.fonts/calibriz.ttf: Calibri:style=Bold Italic