Upgrade to Pi-hole 2024.05.0
On all three nodes I upgraded Pi-hole successfully by means of fully automated Watchtower Docker container update.
On the CentOS 7 VM i had to recreate a sym-link to /etc/lighttpd/conf-enabled/99-unconfigured.conf within the container.
ln -s /etc/lighttpd/conf-available/99-unconfigured.conf /etc/lighttpd/conf-enabled/99-unconfigured.conf