LibreOffice - Calibri font availible when opening a doc but not in dropdown

You have to install it:

1. Install Microsoft's classic TrueType fonts: sudo apt install ttf-mscorefonts-installer

2. Install Microsoft's newer ClearType fonts:

   • which includes: Constantia, Corbel, Calibri, Cambria, Candara, and Consolas
   • make fonts directory: mkdir ~/.fonts

   • wget -qO- http://plasmasturm.org/code/vistafonts-installer/vistafonts-installer | bash

3. Then close and open LibreOffice, if open while you installed these fonts.

Source:

http://www.pcworld.com/article/2863497/how-to-install-microsoft-fonts-in-linux-office-suites.html

The image that you've included with your question shows that the name of the font is in italics. This means that the named font is not installed, and an automatically selected substitute has been used instead. If you hover the cursor over this italicised font name you may see a comment to this effect.

If you don't wish to install the missing font, you can edit the Style to specify a font that is installed (right-click within a paragraph, and choose 'Edit Paragraph Style...' from the bottom of the dropdown menu).

In Microsoft Office the same thing happens with missing fonts, but there's usually no indication that a font substitution has occurred.