System laggy since upgrading to 20.04

I upgraded to 20.04 LTS about a week ago and have been experiencing very laggy performance since.

There seems to be a slight but perceptible lag with keyboard input and with general performance (moving between tabs in my browser etc).

I'm running the Gigabyte GeForce GTX 1050 Ti Windforce OC 4G as my GPU.

And I'm using the following NVIDIA driver: nvidia-driver-440 (proprietary, tested) automatically installed during installation.

Desktop environment: LXDE.

How can I go about diagnosing whether this is an NVIDIA driver issue, a hardware issue, or something else?