If you use UniFi Protect you can't disable it without losing access to your video feeds in the app.
Yes, I upgraded from Unifi Video to Unifi Protect (by purchasing a Cloud Key Gen 2 Pro), and was pretty dismayed that you have to allow outside access (via the Unifi cloud) to use the cameras in the app. For the hypothetical reason that this might be cracked once. This was two weeks ago... didn't expect it would happen so soon.