Flash is no longer being developed for Linux, and the newest versions are only available built-in to Chrome. If you use the Chromium browser, you can extract the Flash plugin from Chrome and use it. If you use Firefox, you’ll need to change to a different browser if you want the latest versions. If you use Chrome, as long as your browser is up to date, you’re good to go.
The package name will be “pepperflashplugin-nonfree”, but it is a free plugin.
8 Type .sudo update-pepperflashplugin-nonfree and press ↵ Enter.