I solved this for my system by removing the Calibri font, installing Carlito, which is "metric-compatible with Calibri" and is packaged with "a mapping entry to fontconfig (local.conf)," refreshing my font cache, and restarting LibreOffice:
$ rm ~/.fonts/microsoft/CALIBRI*
$ sudo apt install fonts-crosextra-carlito
Here's a before and after with Microsoft at the top and Carlito below:
You can do the same with Caladea for Cambria with
fonts-crosextra-caladea and you can use Croscore fonts Arimo, Tinos, and Cousine for Arial, Times New Roman, and Courier New with
See my full post for more details.