On a whim, I tried to install Linux Mint 18 KDE from a DVD instead of USB. Despite a few problems…it worked. Didn't mess up my grub menu, rendering my computer un-bootable!
Want to try out Plasma…KDE 5. I had stability problems in the past, but so far so good.
Perhaps this would have worked for Antegros also!
Installed Linux Mint 18 Cinnamon also. ffmpeg is back!