Step 1: Enable Ubuntu Canonical Partners Repository
In order to install the latest Flash plugin, you need to have the Canonical Partners repository enabled on your system. Open your Ubuntu Terminal. Then enter the following command as root in order to enable the repository:
$ sudo add-apt-repository "deb http://archive.canonical.com/ $(lsb_release -sc) partner"
The next step is to update your system repositories so that the latest available version of a software can be installed. Run the following command as root in order to do so:
$ sudo apt update
Now, your repository is in line with the latest package available in the Internet’s Canonical Partners’ repository.
Step 2: Install the Flash Plugin through the apt package
You can install the Flash Plugin easily by running the following command as sudo in your Linux Terminal:
$ sudo apt install flashplugin-installer
Step 3: Enable the Flash Player through the Adobe website
Open one of the available web browsers on your system. Restart the web browser if it is already open and then open the following link on the official Adobe website.
https://helpx.adobe.com/flash-player.html
You will see a few points in the Flash Player Help. Move to point number 5 and see if you can view an animation running in the window:
If not, click on the Run Adobe Flash link on the animation window in order to allow Adobe Flash to run on the browser.
See original article contains more details on https://vitux.com/how-to-install-adobe-flash-player-on-ubuntu/