I’ve had to stop adguardhome and use the DNS option under More Settings, however I cannot use my NextDNS ID this way; I have tried to change the back-end config files for Doh with no success.
I upgraded the firmware to the latest release, I kept all the settings the same.
How did I do what? Changed the back-end config files? I ssh into router and modified the NextDNS address in the public-resolvers.md file as you suggested in this post here.
Happened to me as well, it was because I have updated adguard in adguard settings page and then flashed 4.0.1 beta1 firmware with keep settings which restored the old binary but kept the adguard settings which is not compatible with old bersion due to a schema change.
I got it working by manually downloading the 107.7 binary from adguards github.
its the armv7 file, I extracted it on my pc using 7zip and use sftp to transfer the binary to router.
replace /etc/AdGuardHome/AdGuardHome binary with the new one and it should work.
Ended up doing factory reset. I messed a lot of things up and I had the adguardhome setup wizard to deal with which I couldn’t get pass figuring out the DNS port 53 issue. I really appreciate your advice/help!