Another way is to create a custom systemd service.
Copy /etc/ssh/sshd_config to /storage/.config/sshd/sshd_config and edit the Port value (or any other settings).
Then create a file /storage/.config/system.d/sshd-custom.service
Code
[Unit]
Description=OpenSSH server daemon
After=network.target
[Service]
Restart=on-failure
ExecStart=/usr/sbin/sshd -D -f /storage/.config/sshd/sshd_config
ExecReload=/bin/kill -HUP $MAINPID
TimeoutStopSec=1s
RestartSec=2
StartLimitInterval=0
[Install]
WantedBy=multi-user.target
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This is basically a simplified version of /usr/lib/systemd/system/sshd.service
The new service must be enabled with systemctl enable sshd-custom.service and started with systemctl start sshd-custom.service (or reboot).
Once this is working, you can disable the default ssh service on port 22 in the Libreelec gui.