Raspi pi-hole admin just shows webserver default page

That's the correct token.

As you noted, you have Apache running and this is interfering with lighttpd.

[80] is in use by apache2 (Prerequisites - Pi-hole documentation)

lighttpd is configured on your desired port in the lighttpd config file

server.port = 8023

A more reliable and persistent way to move lighttpd to an alternate port appears here:

https://discourse.pi-hole.net/t/lighttpd-daemon-wont-start/44985/13

I recall that this duplicated configuration line will cause problems. The server.port := line in the external conf file will alleviate this conflict.