html5-codecs do not work even if installed from flathub
I have reported #68 (closed) to complain that there is no way for users to get the html5-codecs extension installed unless they first install flathub. We do not and cannot expect users to have flathub installed when installing apps from our gnome-apps-nightly, so that's sad.
But I just realized I do have flathub installed, for fractal stable, and I do have runtime/org.freedesktop.Platform.html5-codecs/x86_64/18.08 installed. But I don't have any extra codecs that should be provided by this extension, e.g. MP4 video does not work in Epiphany. So the extension just doesn't work at all.
We had it working sometime around last summer, but with the old 1.6 runtime. I think it's never worked for us in 18.08 despite many attempts to fix it I've seen fly by on the upstream GitLab.