The attempts at building something compatible like shumway have all been rather unsuccessful.
Even if the code was available, porting it to WASM would probably be a pretty big task.
It would be great to retain access to the huge amount of flash content out there though.
It's possible to play "Prince of Persia" in the browser (through DOSBOX recompiled to Javascript).
It's even possible to play the original Windows 95 (!) Pinball in the browser. Seeing the Windows 95 cloudy boot sequence in a Javascript canvas is disturbing. The game isn't as smooth as native, but it's definitely playable. ( https://classicreload.com/win9x-3d-pinball-space-cadet.html )
Alternative proprietary implementation was rather successful for game development. Sadly Scaleform GFx is now discontinued too and obviously we'll never see Autodesk publish anything under open source license.
This shows we should only allow technologies on the web if they have a clear path to preservation.
I think a similar thing should hold for DRM'ed video. Such videos may be supported on the web, but we should demand they lose their DRM when their copyright expires.