I like Libre Office, It's free Open Source, professional and easy to use. But when I recently wanted to produce a high quality professional piece of wriitng. I found the fonts rather lacking.
Most of the guides that I googled on the web for installing fonts seemed slightly out of date, so I thought I'd write some instructions.
First you will need to download some fonts there are numerous websites and mine were in .ttf format.
The folder to copy the font files into is fond at fonts/ /usr/share/fonts/
So it was just a simple matter of copying the downloaded files into this fonts folder. I didn't have a ttf folder inside the fonts folder so I made one.
I then copied the fonts into this folder using the following command, you may need to type sudo first.
cp -a fonts/ /usr/share/fonts/ttf/
The -a parameter is recursive and makes sure that everything in the folder is copied. It took some experimentation to get the / slashes in the right place.
Then when I restarted Libre Office the new fonts were added