You can try using browser emulators like RetroBrowser (//retrobrowser/) or Browsix (//browsix/) to run older browser versions with Flash Player support. These emulators allow you to experience web content as it appeared in older browsers.
If you stumble upon an old website with a broken Flash title you'd like to play, you can do so by installing Ruffle on your computer. There are browser extensions for Chrome and Firefox. Just install the extension and any Flash content that you run into on the web, new or old, will automatically open in the emulator.