I have a MacMini which has no built-in camera. During the pandemic, I have been doing more on-line teleconferencing (mostly Zoom and Facetime meetings). I have used various cameras and various software to connect them to my computer.
I recently came across Detail, from Detail.co . This application allows you to use your iPhone or iPad as a web camera for your Mac. This is the best solution I have seen yet, and the iPhone has a good-quality camera, so my video looks good.
The Mac application does much more than that, which is both an advantage and disadvantage. It is a disadvantage in that it makes it harder to learn to use. There is a video tutorial on the site. The quick summary is to download the Detail app from the iOS or iPad OS App store on your iPhone or iPad, and also download the app for Macintosh from the web site. The app can work wirelessly, or via a USB cable (recommended).
You may want a tripod adapter for your phone. I bought this one and it seems like a good one. You might want to use that with a small desktop tripod like this, if you don’t have one.
Detail is not free, and they are kind of cagey about the price. I actually don’t know how much or how often they charge. There is a 14 day free trial period. I discovered and got access to Detail through my Setapp subscription, which is excellent for just-in-time discovery of useful, curated apps.