After much tribulation, I finally got Flash Player working in Opera, Opera-Next, and Opera-Beta

I simply downloaded the version 23.0.0.207 from Adobe (.gz version), extracted the libpepflashplayer.so file and installed it as follows:

mkdir /usr/lib/PepperFlash

cp libpepflashplayer.so /usr/lib/PepperFlash/

restart browsers and it worked.