I have an MC 8.1 running on Late 2009 iMac and El Capitan... Yes, I know:). But everything works like a charm as long as I don't use any AVX2 Plug-Ins. When I install one AVID just won't start up at all. Not even the first splash screen appears. And the app is "not reacting". I tried different AVX2 Plug-Ins and it is always the same thing. I deleted the MCstates and uninstalled, reinstalled everything in every possible way with no effect. I changed the rights of the AVX2 Folger also without effect. But I take the .avx file out of the folder and put in on my desktop AVID starts up.
Thank you. And yes, absolutely. But the funny thing is that AVX2 trials and demos I tried stated to be El Capitan compatible. Also when you google it you don't really find the same issues in connection with El Capitan.