In this mode, the browsers run remotely and stream the video to your browser. We are still working on the audio support but hope to have audio support soon. It should be possible to archive Flash in this way, though we could use more help/research in this area.
Once the last version of Flash is released, we'll include the latest browsers that can run it.
If the Mozilla Shumway project or similar picks up again (we hope), Webrecorder can integrate that as well to offer a native JS based Flash-recording and replay.
If anyone is interesting in helping out, let us know!
It might be possible to also run Flash in a mini VM. Who knows, maybe someone will figure it out playing flash in WebAssembly in "legacy mode" which disables a vast swath of file and other security issues. Introducing sandboxing could be one angle, but I'm sure someone far more experienced has already thought of this.