I think I might know what's happening. I believe master (snapshot) currently have the package missing. This could be due to the recent Go 1.18 update.https://github.com/openwrt/packages/pull/18147.
There was some foresight it might be a problem: https://github.com/openwrt/packages/issues/17508, its likely because AdGuardHome doesn't like being built with a different version of Go. Currently 0.107 stable releases require 1.17, but now OpenWrt is using 1.18 in master, which might explain the failure.
Edit: Yeah it is failing in master, there are faillogs for the package: https://downloads.openwrt.org/snapshots/faillogs/arm_cortex-a9_vfpv3-d16/packages/adguardhome/compile.txt