How to setup DoH server failover

it is possible to make it so that only the first dns source is always turned on and only in cases of its unavailability the second spare is turned on ?
Very often there is incompatibility and there is an incorrect definition of dns if two sources work.
it would be cool if there was such a function.
Or can I somehow enable it myself through PuTTY? then tell me how to do it?

If one source of dns works, then there is less 3 megabits of RAM, which has a very good effect on performance. The second dns source is needed as a backup, in case of unforeseen situations, if the first one suddenly stops working. I would like to implement it somehow

or it can pause for 5 seconds, if there is no https response from the first source, then the second dns source is turned on, but the first one should be in priority

please tell me the setting
uci set https-dns-proxy.dns.dscp_codepoint="63"
will help with a priority to the first according to the dns lis t?

(I will answer myself, it did not help)