I’m afraid that this hasn’t worked for me. Xubuntu, actually. I’ve tried several different suggestions, including Adobe’s own APT package and the .tar.gz package. When I installed,
The following packages will be REMOVED: adobe-flash-properties-gtk adobe-flashplugin
and then the new package installed. On the flash-player.html page, step 2 says that it’s not installed (it says the same after the Adobe install too). Step 5: no “Activate Adobe Flash” comes up, no clouds come up in the animation, just a two-circling-arrows icon. If I click on that icon, it refreshes the page to no effect. Rebooting the VM does not help. Would anyone have any suggestions about what else to try?
An answer elsewhere said “browser-plugin-freshplayer-pepperflash does currently not work with recent versions of Firefox”. I uninstalled it and the tree / cloud animation works now. Unfortunately, the Flash game that I want to play still doesn’t work, but at least there’s this much progress.