Hello,
I'm facing a very similar problem and I'm not pretty sure how to solve it.
I'm using a Raspberry Pi 3 B+ running Pi-Hole and Kodi. The modem & router I use is a FritzBox 7590.
Now I wanted to centralize all data of kodi so I can use different systems (Kodi on Raspi/Laptop/Smartphone) using the same data base. I installed MariaDB and created the needed data base inlcuding a specific User to access this data base. So far everything's ok.
I wanted to check (and change a bit) my installation using phpmyadmin (I use Putty on command line and a virtuell desktop as well). I had to realize (after an error occured "[ERROR]: Unable to parse results from queryads.php: Connection timeout (3s)" and a lot of searching in the web): it collides with Pi-Hole because of the same used port, I guess.
To solve this, perhaps I first have to change my local network setting. At the moment all devices in network get redirected to the Pi-Hole (Internet -> Zugangsdaten -> DNS-Server -> Andere DNS-Server verwenden). Until now there was a publicly alternative DNS-Server (for DNSv4 & DNSv6) included, but as I read above, this can make problems, because FritzBox not only uses this alternative dns-server if Pi-Hole isn't reachable (in case it's down, for example) but maybe even when Pi-Hole works fine and blocks specific urls.
So I would have to change this, right? What will be the right configuration in this case (routing from xxx - to xxx)? I want to offer the ad-filtered web-access for all clients in network without the need to change something on client-side itself.
Furthermore: how can I solve the problem with the collision of Pi-Hole and phpmyadmin? As far as I understood, it's not enough to define an alternative port but I have to change the ip-adress for one of them. Which one is better, Pi-Hole or phpmyadmin?
Thanks for help in advance!
Joni