Platform does not inherit the org.freedesktop.Platform.html5-codecs extension
Just tried installing epiphany in a clean environment to reproduce it.
cc @mcatanzaro
➜ ~ podman run --rm -ti fedora:29 bash
[root@8f62c7b7960b /]# dnf install -y flatpak
Fedora Modular 29 - x86_64 216 kB/s | 1.5 MB 00:07
...
Complete!
[root@8f62c7b7960b /]# flatpak remote-add flathub --from https://flathub.org/repo/flathub.flatpakrepo
[root@8f62c7b7960b /]# flatpak remote-add gnome --from https://sdk.gnome.org/gnome-nightly.flatpakrepo
[root@8f62c7b7960b /]# flatpak remote-add gnome-apps --from https://sdk.gnome.org/gnome-apps-nightly.flatpakrepo
[root@8f62c7b7960b /]# flatpak remotes
Name Options
flathub system
gnome system
gnome-apps system
[root@8f62c7b7960b /]# flatpak install gnome-apps org.gnome.Epiphany
Required runtime for org.gnome.Epiphany/x86_64/master (runtime/org.gnome.Platform/x86_64/master) found in remote gnome
Do you want to install it? [y/n]: y
Installing in system:
org.gnome.Platform/x86_64/master gnome 02534d254cb1
org.gnome.Platform.Locale/x86_64/master gnome 5680a719c00c
org.gnome.Epiphany/x86_64/master gnome-apps 2dc014a697f1
permissions: ipc, network, pulseaudio, wayland, x11, dri
file access: xdg-download, xdg-run/dconf, ~/.config/dconf:ro
dbus access: ca.desrt.dconf, org.freedesktop.Notifications, org.freedesktop.secrets
system dbus access: org.freedesktop.GeoClue2
tags: nightly
org.gnome.Epiphany.Locale/x86_64/master gnome-apps 035dce727a3b
Is this ok [y/n]: y
Installing: org.gnome.Platform/x86_64/master from gnome
[####################] 1239 metadata, 24239 content objects fetched; 342544 KiB trans
Now at 02534d254cb1.
Installing: org.gnome.Platform.Locale/x86_64/master from gnome
[####################] 1693 metadata, 5790 content objects fetched; 141943 KiB transf
Now at 5680a719c00c.
Installing: org.gnome.Epiphany/x86_64/master from gnome-apps
[####################] 84 metadata, 476 content objects fetched; 4626 KiB transferred
Now at 2dc014a697f1.
Installing: org.gnome.Epiphany.Locale/x86_64/master from gnome-apps
[####################] 379 metadata, 99 content objects fetched; 2014 KiB transferred
Now at 035dce727a3b.
bwrap: Creating new namespace failed: Operation not permitted
bwrap: Creating new namespace failed: Operation not permitted
bwrap: Creating new namespace failed: Operation not permitted
[root@8f62c7b7960b /]# flatpak update
Looking for updates...
[root@8f62c7b7960b /]# flatpak list -d
Ref Origin Active commit Latest commit Installed size Options
org.gnome.Epiphany/x86_64/master gnome-apps 2dc014a697f1 - 8.5 MB system,current
org.gnome.Platform/x86_64/master gnome 02534d254cb1 - 1.1 GB system,runtime
[root@8f62c7b7960b /]#