Endless OS 3.6.4 was released for existing users yesterday and new users today. It is identical to 3.6.4~beta1.
Updated Flatpak to support extra-data extensions
Flatpak has been updated to support extensions which use the extra-data feature, including the new org.freedesktop.Platform.openh264 extension. This resolves an issue where some apps – including Steam and Spotify – could not be installed from the App Center, failing with an error stating that Flatpak 1.4.2 is required.