Comment 6 for bug 1865218

It can be worked around by manual configuration:

# a2dismod php7.2
Module php7.2 disabled.
To activate the new configuration, you need to run:
  systemctl restart apache2

# sudo a2enmod php7.4
Considering dependency mpm_prefork for php7.4:
Considering conflict mpm_event for mpm_prefork:
Considering conflict mpm_worker for mpm_prefork:
Module mpm_prefork already enabled
Considering conflict php5 for php7.4:
Enabling module php7.4.
To activate the new configuration, you need to run:
  systemctl restart apache2

# apachectl -t
Syntax OK

# sudo service apache2 restart
sudo: setrlimit(RLIMIT_CORE): Operation not permitted

# ls /etc/apache2/mods-enabled/php*
/etc/apache2/mods-enabled/php7.4.conf /etc/apache2/mods-enabled/php7.4.load

# apache2ctl -S
VirtualHost configuration:
*:80 php-fix-lp1865218-mod-php-upgrade.lxd (/etc/apache2/sites-enabled/000-default.conf:1)
ServerRoot: "/etc/apache2"
Main DocumentRoot: "/var/www/html"
Main ErrorLog: "/var/log/apache2/error.log"
Mutex watchdog-callback: using_defaults
Mutex default: dir="/var/run/apache2/" mechanism=default
Mutex mpm-accept: using_defaults
PidFile: "/var/run/apache2/apache2.pid"
Define: DUMP_VHOSTS
Define: DUMP_RUN_CFG
User: name="www-data" id=33
Group: name="www-data" id=33