Q:

Ubuntu 16.04 Error this plugin is not supported. Flash Player

When I try to run flash on any website it says this Plugin is not supported
Specs:
1.9 GiB
Intel® Core™2 Duo CPU E8400 @ 3.00GHz × 2 
Gallium 0.4 on AMD RV620 (DRM 2.43.0, LLVM 3.8.0)
64-bit
155.3 GB 
(I know we have a ancient computer) 
This is the error message.

A:

Install ubuntu-restricted-extras package
Or alternatively flashplugin-installer package.

A:

I had the same error message (on Ubuntu 16.10). Already had ubuntu-restricted-extras and flashplugin-installer installed, but neither Firefox nor Chromium would play the flash stream. 
Installing adobe-flashplugin (and accepting the solution of uninstalling flashplugin-installer) fixed the problem for me.

