dashlite

Now that's impractical, because of cost. There's a wealth of SWF content that will never ever be ported.

An SWF runtime is feasible, it's actually not a very complicated format. The devil is in the details, but a lot of content does not use that many features.

The HTML5 backends are garbage. The workflow isn't streamlined like SWF and none of the Actionscript ecosystem carries over. Adobe just doesn't care about the product anymore.

You're better off using any of the game frameworks with HTML5 export, but from an accessibility standpoint, those are still a notch above Flash.