Great plug-in, Glenn!
Just posting this here if anyone is having problems with the bundled ffmpeg with older versions of macOS.
It wouldn't run on my 10.13 machine, got a dyld: cannot load 'ffmpeg' (load command 0x80000034 is unknown) error.
Solution: replace it with a static build from https://evermeet.cx/ffmpeg/.
Just copy it over here:
/Library/Application Support/Perceptive Automation/Indigo 2023.2/Plugins/HomeKitLink-Siri.indigoPlugin/Contents/Packages/homekitlink_ffmpeg/ffmpeg_binaries/x86/