I have installed opera-stable_37.0.2178.32_amd64 on ubuntu 15.1
It works, but it doesn't read any flashplayer plugin.
I have installed the most recent flashplayer version and it works on other browsers (Firefox).
In opera, typing opera://plugins, I can see Adobe Flash Player - Versione: 22.214.171.1247 - Shockwave Flash 20.0 r0 enabled.
I checked and it did not exist the directory /usr/lib/opera/plugins
I created it by typing " sudo mkdir /usr/lib/opera/plugins" and copied in it the libflashplayer.so file.
It doesn't work anyway.
I like Opera and I would not like to give up with it.