Your debug log shows there is no PHP installed on the device:
*** [ DIAGNOSING ]: php version
[✗] php version could not be detected.
There is also another error:
*** [ DIAGNOSING ]: Operating system
[i] Distro: Debian
[i] Version: 11
[✗] dig return code: 139
[✗] dig response: 139
[✗] Error: dig command failed - Unable to check OS
This is very similar to this post: Pihole -up error: Retrieval of supported OS list failed. dig failed with return code 139. Unable to determine if the detected OS (Raspbian 10) is supported - #8 by jfb