You have a good point here. I would question the wisdom of falling back to Flash, though. Native support of both dash AND hls in web browsers is terrible.
https://caniuse.com/#feat=mpeg-dash
https://caniuse.com/#feat=http-live-streaming
HLS can be done in much the same fashion as described in my article with https://github.com/video-dev/hls.js/tree/master I might do a follow-up with the necessary changes.