Why aren't the fonts I installed on my machine showing up in Inkscape?
When installing fonts, you want to make sure that Inkscape is not open. If you install your fonts and the software is open, just close Inkscape and open it back up for your fonts to show.
Another thing that seems to resolve the issue is to make sure you install the fonts for all users...that is typically what will assure you will see them in Inkscape.
If you do not know how to install fonts, please visit https://jennifermaker.com/fonts