According to the developer, whose team is responsible for the RPM packages of Mozilla Firefox for Fedora and Red Hat Enterprise Linux operating systems, the most requested thing by users was a Flatpak package, which is a universal binary format allowing application developers to distribute their apps across multiple Linux OSes.
While currently ditching the standard Firefox web browser as a Flatpak because it doesn’t bring a lot of benefit at the moment, they created a testing, unofficial Flatpak for the Developer Edition, which is not all that accessible to most Fedora Linux users. The Flatpak is built on Red Hat’s internal build cluster and available at https://firefox-flatpak.mojefedora.cz/.
The Firefox Developer Edition was successfully tested on the Fedora 25, Ubuntu 16.10 (Yakkety Yak), and openSUSE Tumbleweed distributions. However, before getting excited and installing it, you should be aware of the fact that it’s currently not sandboxed.
This means that the web browser will have full access to your Home directory, which might compromise your system’s integrity. If you want to test it, you’ll need Flatpak 0.6.13 or later installed on your distribution.
Submitted by: Arnfried Walbrecht