How to downgrade Unifi Controller Software

1. You need a backup file from the version you want to downgrade. If you haven`t, you can stop here.
2. SSH into your controller

ssh {user}@{controller-ip}

1. Removed existing downloads

rm -f unifi_sysvinit_all.deb*

1. Uninstall current controller package

apt purge unifi -y

1. Download old controller package (replace version in url with your needs)

wget https://dl.ui.com/unifi/6.5.54/unifi_sysvinit_all.deb

1. Install package

dpkg -i unifi_sysvinit_all.deb

1. Remove download

rm unifi_sysvinit_all.deb

1. Access UniFi Controller WebUI and restore backup