OBS is free and open source software that will provide various filters and effects you can apply to an input such as a webcam. It will generate an output stream which any app will think is a webcam.
In this way you can apply custom masks, overlays, zoom in, add a title, change colours, change scenes between multiple cameras, or share your screen, change the background, and lots more.
See https://www.xda-developers.com/how-i-use-obs-to-reframe-my-webcam