The issue I am facing:
The admin interface just redirects back to the login page after putting my password in and clicking login no errors/messages on the page.
Details about my system:
Debian 11 using Nginx to reverse proxy the lighttpd server
What I have changed since installing Pi-hole:
New install nothing changed after installing pi-hole other then changing the nginx config to reverse proxy the lightpd server and the lighttpd server config to change the port to 8081
Didn't use the nginx configuration help on the pi-hole docs site cause i wanted to keep the admin page separate from my main page
Put the port number in external.conf instead in order to retain it. See this paragraph and the slightly different syntax (ignore the Caddy stuff).
It sounds like a cookie is not being set to record that you are authenticated, meaning you redirect from /admin/login.php to /admin/index.php and are not authenticated which will make Pi-hole bounce you back to /admin/login.php.
I've not used nginx in detail but found this, talking about Chrome specifically not setting domain cookies for IPs, only for FQDNs. Leaving aside that specific issue, you don't have any cookie directive in your nginx config; will that be the cause?
Is it happening in multiple browsers? If the browser thing ends up being related try pi.hole in place of 192.168.0.69 and accessing it by that domain instead of the IP.
###############################################################################
# FILE AUTOMATICALLY OVERWRITTEN BY PI-HOLE INSTALL/UPDATE PROCEDURE. #
# ANY CHANGES MADE TO THIS FILE AFTER INSTALL WILL BE LOST ON THE NEXT UPDATE #
# #
# CHANGES SHOULD BE MADE IN A SEPARATE CONFIG FILE: #
# /etc/lighttpd/external.conf #
###############################################################################
I forgot to mention I am already using my own domain name. I went ahead and added that information about chrome not accepting cookies unless from an FQDN and I've also rolled back the edits to the default lighttpd.conf and put them into the external.conf.
It worked and still does work in Chrome but my preferred browser is Firefox(in which it doesn't work)
Interestingly it doesn't affect the mobile Firefox browser. I'll have to look into my desktop Firefox browser settings to see what is going on.
Firefox must have had an old cookie from a previous attempt at installing and setting up pihole that was interfering with pihole accepting my sign-in. I deleted the cookie data for my domain and it allowed me to log right in as expected