I have attempted to install several fonts today. I followed all of the instructions above, and it seems that the fonts are installing. However, when I look in the list or in applications, none of them show up.

Are the fonts compatible with macOS Catalina? You did not mention just dropping the fonts into your local Library. I know either method works for me on Catalina 10.15.1. If you are attempting to install Windows only fonts, that may be an issue.

In Catalina, you double-click on the individual font face, and Fontbook will open a small window with an Install Font button. I can immediately (< 15s) open Pages and the font that I just installed appears on the Font menu. This is true with LibreOffice v6.3.3.2 also.

If you have a font with a large number of font faces, you can just drag and drop the enclosing folder into your local Fonts folder (/Users/yourname/Library/Fonts) and the same result occurs as in the first paragraph — the new fonts are quickly recognized in applications. Saves the tedium of double-clicking individual font faces per the first paragraph.

Reboot by holding the shift key to throw you into Safe Boot mode. Then reboot normally. That cycle would have rebuilt the System font database, and the font accessibility should be a thing of the past. I didn't have to do this with Catalina.

Are you also suggesting that simply dropping the OTF fonts into your local Library did not work either. If that is the case, then I have no other suggestions for you, as there are only two means of installing fonts on Catalina, which have been discussed here.

You are welcome, and though you should not have to reinstall the O/S, it is good that you have it solved.