As the Ruffle page says right on it, Action Script 3 API support is at 5%. If they had the original source code and only had to cross compile to WASM, this would go a lot faster. Which is what OP asked.

Dev here: that "5%" number was way overdue, I just bumped it :) After over a year of slowly adding bits and pieces without anything actually working, we finally had a breakthrough with some nontrivial games starting to work this month. Still a ways to go though.

Hey, good to hear!

It's much more than that. The homepage hasn't been updated in ages. Recently they had the first fully playable game (Wonderputt): https://www.newgrounds.com/portal/view/577928, with more partially playable.

Still needs work but it's exciting stuff.

What a delightful and relaxing game!

Homestar Runner is doing the same thing. The entire site has been revived using Ruffle.

https://www.homestarrunner.com/

https://z0r.de/0 also uses it to keep its collection of flash loops running.

Edit: Warning some of the loops may be considered NSFW, most have sound.

Ruffle seems to have some issues on Brave on archive.org.

TypeError: Failed to execute 'compile' on 'WebAssembly': An argument must be provided, which must be a Response or Promise<Response> object