There's no way to disable Android Pie's gesture-based navigation on the Pixel 3

With Android 9.0 (Pie), Google revamped its navigation paradigm, reworking the multi-tasking and app-switching interface into a more gesture-based UI. On most devices running Android Pie, the old, three-button interface could be reactivated easily via a toggle found in the settings app.

Hi! Pixel 3 introduces a new pattern that will represent navigation on all Android phones going forward. While change & adapting to new patterns is hard, we believe it's a better navigation pattern & makes app switching a faster experience.
— Made by Google (@madebygoogle) October 9, 2018

This won't be the case with Google's fresh-off-the-oven Pixel 3 handsets, however. In a tweet, the company confirmed that the option to turn off gestures won't be available for buyers of the device, leaving them stuck with the new gesture-nav interface.

Though this new UI was expected to be the default paradigm on Google's new smartphones, it's sure to be a disappointment for those who prefer the older, decidedly simpler button-based interface.

Source: Google (Twitter)