OS - ArchLinux 64bits
SPECS - i3-3220 - 6gb ram
QGIS 3.0.3 installed as follow.
$ sudo pacman -S qgis gdal python-gdal python-psycopg2 python-owslib python-yaml python-pygments
$ yaourt -S python-jinja-time
On the section ALL - do not appear.
On the INSTALLED - do not appear.
As you can see, georeferencer is missing.