Upgrade firmware without a controller:
- Find the correct firmware for your model Unifi AP such as https://www.ui.com/download/software/uap-ac-lite
- Right-click the download and copy the download URL
- SSH to the AP
- For example: Type "upgrade https://dl.ubnt.com/unifi/firmware/U7PG2/6.5.62.14788/BZ.qca956x_6.5.62+14788.230622.2048.bin" (paste the URL from the web download)