This has been announced in December 2022:
Lighttpd Config
There have been some improvements to the lighttpd configuration to prevent the default config from being overwritten on new installs (See #5065 and #5075 ), however existing installs will still use the Pi-hole generated config for the time being. As the line “FILE AUTOMATICALLY OVERWRITTEN BY PI-HOLE” exists in /etc/lighttpd/lighttpd.conf, the file will be overwritten (See here ). All user configuration should be made in external.conf, or make use of the conf.d/conf-available/conf-enabled directories – depending on OS
And it's also mentioned in the Upgrade Notes for Docker Pi-hole
As of 2023.01, if you have any modifications for lighttpd via an external.conf file, this file now needs to be mapped into /etc/lighttpd/conf-enabled/whateverfile.conf instead