Comment by RBerenguel

I’ve been using CamTwist (http://camtwiststudio.com/) for it after checking the alternatives. Even if old-looking it works well (in Catalina and Mojave) and has converted my old iPhone into a good-quality webcam. OBS studio is getting virtual webcam support soon (see a recent post about OBS studio) and will allow for that as well (I have tried the proof of concept implementation)