Kong pro firmware for IPQ806x (R7500, R7800, EA8500, ...)

Hi,
I use dns.adguard.com in my Android phone settings to block ads, and it worked seamlessly on DD-WRT.
However, with OpenWrt (KONG 23.05 NSS), I encounter an issue – no internet on my Android phone unless I disable the private DNS provider. Can you suggest any changes in OpenWrt options to resolve this? I'm a civil engineer, so for networking I prefer straightforward instructions with minimal programming and more GUI adjustments. I appreciate your help!

It's an R7800, connected via a LAN cable to the main router. I also use a WireGuard client, but removing the WireGuard interface doesn't fix the problem.

Edit: The issue only occurs with Kong build even on default settings. Tried the standard OpenWrt build 23.0.5 and I didn't face that issue: [Solved]My phone private DNS provider not working with Openwrt