As someone who has used Linux on the Desktop for 20+ years, I can say with pretty high confidence that open source flash players could not run more than a trivial amount of real world flash content at the end of its life cycle ~10 years ago.

Ruffle.rs looks pretty promising for playing flash.

Adobe still has the editor as Adobe Animate - if they made it more widely available, I think there is a big demographic of designers that would like to make a bit of animation or active graphics that is not being served any more.