Webcams (both integrated and external) are laggy (and have no virtual background support) in Zoom 5.8.0 on Ubuntu 20.04.3

I bought a Lenovo ThinkPad-E15-Gen-2 this summer and installed Ubuntu 20.04.3 (dual-boot alongside Win 10).

I've been experiencing many different problems in Ubuntu, this being one of them.

Google Meet video chats work fine.

However, when using Zoom 5.8.0, my webcam video is laggy*. And when I choose a Virtual Background, it never takes effect.

I've also tried plugging in a Logitech C270 webcam, but it has the same problem on Zoom.

I've reported my troubles to Zoom but haven't heard back.

*When I move my arm, for example, the image of myself on the screen moves after a slight delay, which is enough to be disconcerting.