Comment 9 for bug 1890263

Similarly, the focal -> jammy upgrade process is also confirmed as fixed now, with the jammy update:

###########################################
### Focal Test Case for BUGGY Behavior ###
###########################################
$ lxc launch ubuntu-daily:focal lp1890263-modphp-buggy-focal
$ lxc shell lp1890263-modphp-buggy-focal
# apt-get update; apt-get -y full-upgrade; apt-get -y autoremove
# reboot
$ lxc shell lp1890263-modphp-buggy-focal
# apt install -y libapache2-mod-php7.4
  The following NEW packages will be installed:
    apache2 ... libapache2-mod-php7.4 ... php7.4-common ...
  ...
# do-release-upgrade -d
  - Answer defaults for everything
  - Allow it to reboot when done, and log back in
$ lxc shell lp1890263-modphp-buggy-focal

# lsb_release -sc
jammy

# apt-cache policy libapache2-mod-php* | grep -B1 Installed:
libapache2-mod-php:
  Installed: 2:8.1+92ubuntu1
--
libapache2-mod-php7.4:
  Installed: 8.1.2-1ubuntu2
--
libapache2-mod-php8.0:
  Installed: (none)
--
libapache2-mod-php8.1:
  Installed: 8.1.2-1ubuntu2
--
libapache2-mod-php5:
  Installed: (none)

# result=$(apt-cache policy libapache2-mod-php8.1 | grep Installed: | cut -d: -f2 | xargs)
# [ "${result}" = "(none)" ] && echo "BUG DETECTED"

# logout

$ lxc stop lp1890263-modphp-buggy-focal
$ lxc delete lp1890263-modphp-buggy-focal