Epiphany is not HW accelerated any more on Stretch, but it was not "replaced by Chromium". It's simply a different (and more lightweight) browser.
Video should work again, if you install all gstreamer-1.0 plugins.
Minimal Kiosk Browser (kweb)
Slim, fast webkit browser with support for audio+video+playlists+youtube+pdf+download
Optional fullscreen kiosk mode and command interface for embedded applications
Includes omxplayerGUI, an X front end for omxplayer