Comment 2 for bug 1865218

With a fix landing for LP: #1850933, I thought I'd test upgrading from Bionic to Focal. Unfortunately is doesn't work:

root@ba:~# do-release-upgrade -d
...
libapache2-mod-php7.4: php7.2 module already enabled, not enabling PHP 7.4
Setting up apache2 (2.4.41-4ubuntu2) ...
Job for apache2.service failed because the control process exited with error code.
See "systemctl status apache2.service" and "journalctl -xe" for details.
invoke-rc.d: initscript apache2, action "restart" failed.
● apache2.service - The Apache HTTP Server
     Loaded: loaded (/lib/systemd/system/apache2.service; enabled; vendor preset: enabled)
     Active: failed (Result: exit-code) since Mon 2020-04-13 17:58:23 UTC; 5ms ago
       Docs: https://httpd.apache.org/docs/2.4/
    Process: 29604 ExecStart=/usr/sbin/apachectl start (code=exited, status=1/FAILURE)

Apr 13 17:58:23 ba systemd[1]: Starting The Apache HTTP Server...
Apr 13 17:58:23 ba apachectl[29607]: apache2: Syntax error on line 146 of /etc/apache2/apache2.conf: Syntax error on line 3 of /etc/apache2/mods-enabled/php7.2.load: Cannot load /usr/lib/apache2/modules/libphp7.2.so into server: /usr/lib/apache2/modules/libphp7.2.so: cannot open shared object file: No such file or directory
Apr 13 17:58:23 ba apachectl[29604]: Action 'start' failed.
Apr 13 17:58:23 ba apachectl[29604]: The Apache error log may have more information.
Apr 13 17:58:23 ba systemd[1]: apache2.service: Control process exited, code=exited, status=1/FAILURE
Apr 13 17:58:23 ba systemd[1]: apache2.service: Failed with result 'exit-code'.
Apr 13 17:58:23 ba systemd[1]: Failed to start The Apache HTTP Server.
...

The problem persists after the system is rebooted post-upgrade. It looks like this on the Bionic upgraded to Focal system:

root@ba:~# dpkg -l| grep php
ii libapache2-mod-php 2:7.4+75 all server-side, HTML-embedded scripting language (Apache 2 module) (default)
rc libapache2-mod-php7.2 7.2.24-0ubuntu0.18.04.3 amd64 server-side, HTML-embedded scripting language (Apache 2 module)
ii libapache2-mod-php7.4 7.4.3-4ubuntu1 amd64 server-side, HTML-embedded scripting language (Apache 2 module)
ii php-common 2:75 all Common files for PHP packages
ii php7.4-cli 7.4.3-4ubuntu1 amd64 command-line interpreter for the PHP scripting language
ii php7.4-common 7.4.3-4ubuntu1 amd64 documentation, examples and common module for PHP
ii php7.4-json 7.4.3-4ubuntu1 amd64 JSON module for PHP
ii php7.4-opcache 7.4.3-4ubuntu1 amd64 Zend OpCache module for PHP
ii php7.4-readline 7.4.3-4ubuntu1 amd64 readline module for PHP

root@ba:~# ll /etc/apache2/mods-enabled/ | grep php
lrwxrwxrwx 1 root root 29 Apr 13 17:55 php7.2.conf -> ../mods-available/php7.2.conf
lrwxrwxrwx 1 root root 29 Apr 13 17:55 php7.2.load -> ../mods-available/php7.2.load

root@ba:~# apache2ctl -S
apache2: Syntax error on line 146 of /etc/apache2/apache2.conf: Syntax error on line 3 of /etc/apache2/mods-enabled/php7.2.load: Cannot load /usr/lib/apache2/modules/libphp7.2.so into server: /usr/lib/apache2/modules/libphp7.2.so: cannot open shared object file: No such file or directory
Action '-S' failed.
The Apache error log may have more information.