Announcement: https://blog.archive.org/2020/11/19/flash-animations-live-fo...

> Utilizing an in-development Flash emulator called Ruffle, we have added Flash support to the Internet Archive’s Emularity system, letting a subset of Flash items play in the browser as if you had a Flash plugin installed

I had trouble when adding e.g. https://archive.org/details/gravityrunner-nolimit because there's literally zero documentation on this system that I could find, but the way that it works is that you edit metadata tags (key-value list) and there is some magic/special tags that have an effect on how the item is displayed on the site, like whether to show you the emulator. What you need to set is:

    emulator = ruffle-swf
    emulator_ext = swf

You can find out what others have set by clicking on 'show all' at the download options and choosing the <itemname>_meta.xml file.