# Armbian source: https://github.com/armbian/build/blob/66b0171516297ced0b0fead62c2f2763627176e5/extensions/preset-firstrun.sh

...
echo "PRESET_NET_WIFI_SSID='MySSID'" >>"${SDCARD}"/root/.not_logged_in_yet
echo "PRESET_NET_WIFI_KEY='MyWiFiKEY'" >>"${SDCARD}"/root/.not_logged_in_yet

# Set PRESET_CONNECT_WIRELESS=y if you want to connect wifi manually at first login
echo "PRESET_CONNECT_WIRELESS=n" >>"${SDCARD}"/root/.not_logged_in_yet # <-- THIS !!!!############33
...