Pushing the downloaded firmware file to the device using a TFTP client. UniFi - Advanced Updating Techniques - Ubiquiti Help Center
: A recurring community concern involves firmware updates causing memory exhaustion or "soft-bricking" consoles like the UDM Pro, requiring manual TFTP recovery or re-flashing . The Download Portal (UI.com) Unifi Firmware Manual Upgrade/Downgrade ubiquiti firmware download
For the vast majority of modern deployments, firmware is not "downloaded" by the user in the traditional sense. Pushing the downloaded firmware file to the device