I have spent a few days trying to fathom out why Opera Dev doesn't load Flash.

Despite copying the latest libpepflashplayer.so (plus manifest) to various locations specified in pepper_flash_config.json (below) as well as ~/.local/opera/plugins and ~/.mozilla/plugins etc it just doesn't load. Firing up Opera Stable 42.0.2393.94 on the same machine and it all works fine although Opera reports the version as 99.999.999.999:

"
Adobe Flash Player
Version: 99.999.999.999
Shockwave Flash 99.999 r999
Location: /usr/lib/adobe-flashplugin/libpepflashplayer.so
Type: PPAPI (out-of-process)
"

The Adobe Flash page (http://www.adobe.com/uk/software/flash/about/) reports it as being the latest:

"You have version 24,0,0,186 installed"

It has all been working fine in Opera Developer for the last year so not sure what has changed.

Cheers

cat /usr/lib/x86_64-linux-gnu/opera-developer/resources/pepper_flash_config.json
{
"PepperFlashPaths" : [
"/usr/lib/adobe-flashplugin/libpepflashplayer.so",
"/usr/lib/pepperflashplugin-nonfree/libpepflashplayer.so",
"/usr/lib/PepperFlash/libpepflashplayer.so",
"/usr/lib64/PepperFlash/libpepflashplayer.so",
"/usr/lib/chromium-browser/PepperFlash/libpepflashplayer.so",
"/usr/lib/chromium/PepperFlash/libpepflashplayer.so",
"/usr/lib64/chromium-browser/PepperFlash/libpepflashplayer.so",
"/usr/lib64/chromium/PepperFlash/libpepflashplayer.so",
"/opt/google/chrome-beta/PepperFlash/libpepflashplayer.so",
"/opt/google/chrome-unstable/PepperFlash/libpepflashplayer.so",
"/opt/google/chrome/PepperFlash/libpepflashplayer.so"
]
}

Version: 43.0.2431.0 - Opera is up to date
Update stream: developer
System: Ubuntu 16.04.1 LTS (x86_64; LXDE)
Browser identification

Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2914.3 Safari/537.36 OPR/43.0.2431.0 (Edition developer)