I managed to figure out how to bypass the cert verification in dbconfig-mysql (named on the tin as dbconfig-common) and got my appliance set up!

1. apt install dbconfig-mysql before installing the PhpMyAdmin package

2. In /usr/share/dbconfig-common/internal/dbc-mysql, in both sections where temporary my.cnf is defined, set ssl-verify-server-cert = off right below the port = line.

3. to install PhpMyAdmin, run DEBIAN_PRIORITY=low apt install phpmyadmin and follow the prompts

4. In /etc/phpmyadmin/config.inc.php add the following line directly under $cfg[‘Servers’][$i][‘host’] = $dbserver;:

   $cfg['Servers'][$i]['ssl'] = true;
   $cfg['Servers'][$i]['ssl_verify'] = false;