Q: Looking for a fix: Major OSX updates on iMac kill ability to use external screens or speakers (AGAIN)

Apple put out a security update. I did the usual acceptance, and it turned out to be a bigger one, requiring a reboot and much time.
Once again, the iMac no longer "sees" any options for external screens or speakers. I cannot choose them or search for them. The screen does the usual "blink" it used to do when switching screen setups, but it just returns to its regular state, instead of providing options or sending the signal to my tv/screen.
Help?