I think this may not be a strictly Opera issue but nevertheless, Opera is one of the browsers getting affected.
I did a fresh install of Kubuntu 19.10 yesterday. During installation, I did check the option to install thrid-party codecs. After the OS was up & running, I installed latest version of Opera as well as Vivaldi browsers.
In both browsers, I am not able to play online video content which requires Flash I guess. Videos on Twitter don't work as wll as vidoes on most news websites.
I decided to check availability of libffmpeg.so and copy the same to Opera's installation directory. Funny thing, I cannot find "chromium-browser" folder in usr/lib/.
I installed Chromium browser from the default Software Store/Package manager but it installed the snap version of it. After installation I still can't see a folder "chromium-browser" in usr/lib/
Further, I installed "Transitional package - chromium-codecs-ffmpeg -> chromium-ffmpeg snap" codecs separately but it seems to have made no difference.
Bottom line, I still cannot play flash videos on both Opera & Vivaldi browsers.
I guess I can use Chromium browser temporarily till the problem is fixed but I prefer to use Opera.
I opened a new thread to help out other Opera/Vivaldi Ubuntu 19.10 flavors users who may in the same boat as I am. Further, I will try to post this on Kubuntu forums as well, but hoping some one can provide resolution ASAP.