I can confirm that is setup on my pihole.You need to ensure for Pihole to be configured to LISTEN on all local interfaces
Your settings look similar to mine.
I seem to be missing the 192.168.0.0/24 assuming this is the IP of the modem in bridgemode.
Your PI has 192.168.2.x as IP? Trying to understand which is which in your wireguard setting.
I guess I will start over by resetting modem and Fritzbox to start fresh with default settings.
My understanding is, the only required adjustments after reset are to set up port forwarding of 51820 on both (modem -> Fritzbox IP and Fritzbox -> PI hole IP) and disable ipv6 on the Fritzbox.
Or is there anything else to take into consideration like setting the PI IP as the fritzbox' DNS?
Or setting a static IP of the Fritzbox to match the PI IP address range (my PI has a static IP of 192.168.200.2 so should the Fritzbox be set to 192.168.200.x), my modem has 192.168.0.1?
Or should the Fritzbox get its IP via DHCP from the modem leading to 192.168.0.2 and therefore not matching the address range of the PI.
In the meantime and to be sure I stop messing/guessing around, could you post all (your) relevant modem (in bridg mode) and Fritzbox settings to be sure I am not misconfiguring them. I have a tendency to do so as you rightly noticed
Hope this isn't too much to ask for as you probably have other things to do as well.
I just want to solve this once and for all and promise to be quiet afterwards