The presence of a DNS server on a host on the local network is
advertised or can be discovered thanks to the mDNS/DNS-SD protocol
(avahi-daemon on Linux). This protocol is also implemented on Android,
with the restriction that the address name must end with ".local". I had
to change the name of my local server to follow this rule.
I've read that this feature and this restriction are implemented in
the libc. It works with all browsers, including the Samsung's and
Google, while I'm pretty sure at least Google uses DoH. But the browsers
are clever enough to detect the ".local".
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