Ruffle.rs and Gnu Gnash are decent emulators, plus Newgrounds had its own player you can install. If you have flv files you can upload them to the internet archive and if you set it up properly, they will be playable with ruffle.rs in the browser, no plugin needed.

https://blog.archive.org/2020/11/22/flash-back-further-thoug...

I don't have a copy of my favourite cartoon from years ago - The Pygmy Shrew - but there is a "ruffle-ised" version of it here:

https://www.newgrounds.com/portal/view/699

However, I can't download the file to upload it to the internet archive. Any tips? (It is, actually, available as a vid file on YT, too, but the original was an flv - here is the YT version: https://youtu.be/d5LA3i_XrVU )

Searching the source code for swf real quick gets me https://uploads.ungrounded.net/0/699_Pygmy_Shrew_1.swf

You can also use your browser's dev tool's Network tabs to watch it download the swf file when you hit play.

Yes. Thanks for that.

Along with Ruffle, there's also Flashpoint, a project to curate an archive of every flash game and animation on the internet. (https://bluemaxima.org/flashpoint/)

You could always use an older version of a browser for the specific purpose of playing those games. It's not great but it works (I have done that with an old version of Firefox for java web applets)