O.K. as I wrote, it depends on the user what they choose

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DNS over HTTPS can be implemented as a plugin and can be further improved (fixes, improvements, ...). Another reason is the absence of free FLASH in older routers, so as a plugin is probably a good idea.
Observe carefully LOG, because a bad validation message appears from time to time, exceeding DNS packet size and STUBBY has a MX record problem (not always).