Use your smartphone camera as a webcam, via OBS Virtual Camera.

Display full-screen camera feed without any user interface on your iPhone

1. Open https://phone-as-webcam.netlify.app/ on your phone.
2. Click "Capture Back" for the back-facing camera
3. Click "Full screen" to make the video feed full-screen. Optionally double tap on the video to completely fill the screen.
4. Enable Airplane/silent mode on your phone to disable push notifications
5. Connect your phone to your computer using a charging cable. For iPhones, this is a Lightning cable. For Androids, this is usually a USB-C or Micro-USB cable.

Mirror your phone screen as a virtual camera on Mac/Windows/Linux/Etc.

1. Download, install, and open OBS Studio
2. Set the right canvas resolution in OBS Studio settings by clicking "Settings" and then "Video". "2436x1125" works well for an iPhone 12 Pro.
3. Add "Video Capture Device" as a new source in OBS studio by clicking + under sources. Use any name and select your phone as a device
4. Start Virtual Camera by clicking "Start Virtual Camera"
5. Your phone screen should be mirrored in Zoom, Google Meet, or others if you select "OBS Virtual Camera" as your camera.

Main inspiration taken from https://github.com/apancik/iphone-as-a-webcam.