How a device finds encrypted DNS by itself

a lookup for _dns.resolver.arpa, a name reserved for ... asking whether an encrypted version exists, and where it can be reached

Neat! Let's try: nslookup _dns.resolver.arpa

    [mine] unblound.lan can't find _dns.resolver.arpa: Non-existent domain 

    [1.1.1.1] can't find _dns.resolver.arpa: Non-existent domain

    [8.8.8.8] No internal type for both IPv4 and IPv6 Addresses (A+AAAA) 
    records available for _dns.resolver.arpa

    [9.9.9.9] Name:  _dns.resolver.arpa

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