I just want to put this in there for those who may be searching for help.
After I upgraded to Ubuntu 19.10, my localhost server, which I use for a number of databases, quit rendering PHP pages. HTML continued to work. I found this page, Apache PHP no longer working after upgrading to 19.10 from 19.04, but in my case all that was necessary was to again enable php with apache2, thus:
sudo a2enmod php7.3 (or whatever last digit).
Following this everything works again. You may need to follow the rest of the instructions and reinstall everything.
Also note that 19.10 uninstalls phpmyadmin. You can reinstall it following the instructions here.