- You need a backup file from the version you want to downgrade. If you haven`t, you can stop here.
- SSH into your controller
ssh {user}@{controller-ip}
- Removed existing downloads
rm -f unifi_sysvinit_all.deb*
- Uninstall current controller package
apt purge unifi -y
- Download old controller package (replace version in url with your needs)
wget https://dl.ui.com/unifi/6.5.54/unifi_sysvinit_all.deb
- Install package
dpkg -i unifi_sysvinit_all.deb
- Remove download
rm unifi_sysvinit_all.deb
- Access UniFi Controller WebUI and restore backup