I remember the last time I tried to find a cheap webcam that works on linux, I gave up pretty quickly and just used my laptop for video calls. Saw this guide to build one with a zero 2, had a spare board in my parts drawer so thought why not. I'm surprised by the quality of it. I've been using it for work meetings.
I've heard of Droidcam, which needs you to install an app on your phone, as well as one on your computer and then lets you use your phone as a webcam.
Also Android 14 has a webcam mode built in when you plug your phone into your computer, though idk if this is just a Pixel specific feature