I have this same problem on my iMac Pro running Big Sur. I have always used MacPorts, not Homebrew, and I already have FFmpeg installed. FFmpeg on my machine is in directory /opt/local/bin and this directory is listed when I do PATH from terminal on the Mac. Mathematica 12.2 seems unable to find my copy of FFmpeg and I get the message about a "lite" version of FFmpeg being used when I try to run VideoCombine. I tried adding /opt/local/bin to Mathematica's $Path list, but this did not resolve the problem.

I don't want to install FFmpeg with Homebrew as I understand that it is well documented that MacPorts and Homebrew do not play well together on the same machine. I have too many other applications working just fine with MacPorts to switch to Homebrew at this time. How can I get my MacPorts version of FFmpeg to work with VideoCombine? Is there some alternative to the Homebrew version of FFmpeg which I could install to make VideoCombine work correctly?

I had the same issue in my Mac. It was solved installing ffmpag.

I don't disagree, Robert. However, 1) our Video functionality is still marked as "Experimental". We are still trying to better optimize such workflows and automatic installation of FFmpeg at least on some platforms is under development. 2) one of the main reasons why Mathematica is not shipped with a full version of FFmpeg is because several video codecs are patented and dealing with those patents is a rather large project on its own. We may as well go for that fight at some point, but it's not today's task.