[nebul]

Well, I'm a few days late but I'm going to leave this here if it can help someone else.

If Ubuntu works like Fedora in this regard, it probably switched from Wayland to Xorg when you installed the proprietary Nvidia driver. The Wayland session supports touchpad gestures natively, but the Xorg one doesn't. You can install something like libinput-gestures[1] to replicate the functionality, with the caveat that the gestures won't be triggered until you lift your fingers off the touchpad. (On Wayland the interface reacts to the gestures as you swipe.)

Ubuntu switching 'silently' to Xorg is actually working as intended because Nvidia's support for Wayland was somewhat experimental until very recently. It's getting better though, and it's now officially supported on Fedora 35.

[1] https://github.com/bulletmark/libinput-gestures