Step-by-step – Flash Plugin Ubuntu Mate 20.04 Installation

Installing

2. 2. Installing Flash Plugin

   Then to Install Flash Plugin for Ubuntu Mate
   Simply play:

   sudo apt install pepperflashplugin-nonfree

   Authenticate with the User Admin Pass.
   If Got “User is Not in Sudoers file” then see: How to Enable sudo.

3. 3. Testing Flash Plugin

   Finally, to Check the Plugin is Correctly Installed
   On Firefox point to address:

   about:plugins

   On Opera:

   opera:plugins

Ubuntu Best Software Installation Guides:
Best Software to Install on Ubuntu Mate.