After first reboot the internet seemed down in firefox.
I have a freshly installed Manjaro with M-A on my new SSD.
First DE was xfce. Then after some issues with lightdm I installed GDM and Gnome.
On the notification center the wifi was appearing normal. Though no connection in FF.
I restarted NetworkManager service and connection came back up.
I have FF crash 4 times until now (all of them) trying to go to Manjaro Github page from a bookmarl link (Edit: also the main page of github).
The forum and another (blog) page did not crash FF.
I can't say where all the above come from.
OT: BTW I loved Gnome in Testing and decided to give it a good try for my main DE.