UniFi - How to Change the Controller Version on UDM v1.7+ via SSH
Connect to the Dvice by ssh
# ssh root@192.168.1.1Enter UniFi OS Shell
# unifi-os shellDownload the Package
# curl https://dl.ui.com/unifi/5.14.9-393d589aeb/unifi_sysvinit_all.deb -o /tmp/unifi_sysvinit_all.debInstall and remove it
# dpkg -i /tmp/unifi_sysvinit_all.deb && rm /tmp/unifi_sysvinit_all.debLeave the Shell and logout from your device.