Firefox Nightly for Linux has been compiled with GTK+3 and the stable version of Firefox 42 may be the first one to be released with GTK+3.
Firefox Nightly 43.0a1 has been recently released, bringing a less intrusive way for showing the fullscreen notifications on YouTube, among other changes, and the fullscreen notifications will not require the user’s permissions every time they’re displayed.
For more info, see the demo video below:
Up to date packages are available via the Firefox Nightly PPA, so installing the aurora version of the internet browser on Ubuntu is easy. Just add the PPA to your system, update the local repository index and install the firefox-trunk package:
$ sudo add-apt-repository ppa:ubuntu-mozilla-daily/ppa
$ sudo apt-get update
$ sudo apt-get install firefox-trunk
Optional, to remove firefox-trunk, do:
$ sudo apt-get remove firefox-trunk
The installation instructions should work on Ubuntu 15.04 Vivid Vervet, Ubuntu 14.04 Trusty Tahr, Ubuntu 12.04 Precise Pangolin, Linux Mint 17.2 Rafaela, Linux Mint 17.1 Rebecca, Linux Mint 17 Qiana, Linux Mint 13 Maya, Pinguy OS 14.04, Elementary OS 0.3 Freya, Elementary OS 0.2 Luna, Deepin 2014, Peppermint 6, Peppermint 5, LXLE 14.04 and Linux Lite 2.