Hi! Here is solution for Opera 43. (Kubuntu 16.04 x64)

1. We need to update Chromium browser to 56.0.2924.76 version (Opera 43 use this version of Chrome engine)
2. Add repository - sudo add-apt-repository ppa:canonical-chromium-builds/stage
3. Update system - sudo apt update
4. Chromium must updated to 56 version
5. As recently as advised tyrion-ua:
   Copy the libffmpeg.so file from the library (/usr/lib/chromium-browser)
   Replace the libffmpeg.so file in the browser folder (/usr/lib/x86_64-linux-gnu/opera) with this file.
   Restart the browser.
   Now Opera plays videos from Twitter, Instagram, etc.

Thank you in-tensive. After a little hokey pokey I got this to work. Thank you for helping me learn a little more about Linux and how to fix this very annoying bug.