Blast, I have all sorts of Debian releases running but not the Bullseye lite release yet.
How did you configure networking like hostname and IP etc?
Did you do it the old fashioned way in /etc/network/interfaces ?
Usually if you have 127.0.0.1 or similar in resolv.conf, it would mean you have a stub resolver running for caching. Bucking_Horn would be able to see in the debug report.
Your debug log shows that your Pi-hole is neither using your FritzBox as its sole upstream, nor is Conditional Forwarding enabled, nor is it acting as DHCP server, nor are there any local DNS records.
Therefore, your Pi-hole has no means of knowing about local hostnames.
You would have to opt for any of the above (or a combination) to see local hostnames.
For now, easiest would be to point your Pi-hole to just your FritzBox, and configure your FritzBox upstreams to 188.8.131.52 and 184.108.40.206 (via Internet|Zugangsdaten|DNS Server).
In that configuration, also make sure that Never forward non-FQDN A and AAAA queries as well as Never forward reverse lookups for private IP ranges are unticked.
Please correct me, but AFAIAAO, Debian *.isos are net installation images, i.e. they prompt you for packages to install during initial installation.
As I've alluded to previously: Would you remember which networking tools you picked? Perhaps you have missed to install a tool for managing resolv.conf?
The link you provided suggests a certain such package:
From your debug, your current resolv.conf is missing the tell-tale generated by comment from resolvconf, and it also still points to Pi-hole:
okay, i can do that. until now i had pihole directly using 220.127.116.11 as upstream dns server. i will now set it up so that it uses the fritzbox as upstream and the fritzbox then uses 18.104.22.168.
how do i do that?
thats right. my .iso file is only 300mb
i did not select any network packages during installation, but i have now manually installed one. resolvconf.
now there is also something in /etc/resolv.conf, namely the following:
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
# DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
# 127.0.0.53 is the systemd-resolved stub resolver.
# run "resolvectl status" to see details about the actual nameservers.
so i can work with this now. i found instructions on the internet to use this. so now i know how to add nameservers to resolv.conf and have them stay..
yeah! it works! thank you so much!
i reinstalled the pihole and set the upstream dns to the router and set the dns server in the router to 22.214.171.124. + Never forward non-FQDN A and AAAA queries and Never forward reverse lookups for private IP ranges disabled. now everything works. everything is filtered and i see the hostnames.
thank you! thank you for pihole and this support.
thank you really!