I've seen several articles about using your smartphone as a webcam.
Some of them even mention Linux.
I run Zoom on an old Nexus smartphone (no SIM). The phone has a decent
camera and mike, and gives more flexibility for the location than my desktop
but has to be plugged in to the charger.
Using smartphones as webcams on Fedora requires building and installing
a driver (which is why I have experience with MOK's for secure boot). I got it
working, but never bothered trying it with Zoom.