> "Please install Vapoursynth via Homebrew"
this message is in fact depends on the existence of /usr/local/opt/vapoursynth/lib/libvapoursynth-script.0.dylib
do you have everything (Homebrew) installed in /usr/local ?
just updated an M1 MacMini to 11.1 and reinstalled x86 Homebrew - everything work as usual