But I was clueless to these poor experiences since I hadn’t tested these scenarios. Fortunately, my app was just released, and only to a beta crowd.
To test the absence of Flash Player, you can download a Flash Player Uninstaller and uninstall Flash Player. I’m not sure what the best way is to install and test an old version of the Flash Player; I just had a virtual machine that had an old version on it, so I used that because it was convenient. If you google for “download flash player 8“, there are some non-Adobe links that appear to be valid links, but I did not try these.
Adobe has a Flash Player Detection and Installation support page that is helpful as well.