Fallback & High Availability with nextdns-cli

Hello there,

I'm planning to install nextdns-cli on my 2 RPis and to use them in High Availability using keepalived (router DNS set to keepalived IP).

I'm using currently AdGuardHome, configured with more resolvers (ie OpenDNS & Cloudflare).

What will happen to my HA nextdns-cli installations, if NextDNS goes down? The network served by the 2 HA RPis will be down.

Is there a way to set a fallback (on nextdns-cli) to another DoH provider in case NextDNS is not able to reply to queries?

For example, my FritzBox is able to fallback to standard DNS if the DoT host is unreachable.

Thanks!