SSHd now uses socket-based activation (Ubuntu 22.10 and later)

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in README.Debian you write

mkdir -p /etc/systemd/system/ssh.socket.d
cat >/etc/systemd/system/ssh.socket.d/listen.conf <<EOF
[Socket]
ListenStream=2222
EOF

this makes sshd listen on port 2222 and port 22.
I think you should mention that for sshd to listen n 2222 only you need to do this:

mkdir -p /etc/systemd/system/ssh.socket.d
cat >/etc/systemd/system/ssh.socket.d/listen.conf <<EOF
[Socket]
ListenStream=
ListenStream=2222
EOF

quote from man systemd.socket

These options may be specified more than once, in which case incoming traffic on any of the sockets will trigger service activation, and all listed sockets will be passed to the service,
regardless of whether there is incoming traffic on them or not. If the empty string is assigned to any of these options, the list of addresses to listen on is reset, all prior uses of any
of these options will have no effect.
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