Instalación del navegador web Brave (ungoogled-chromium)

calculate ~ # emerge net-libs/nodejs-bin
Local copy of remote index is up-to-date and will be used.
Calculating dependencies… done!
[ebuild N ~] net-libs/nodejs-bin-6.9.4

The following keyword changes are necessary to proceed:
(see “package.accept_keywords” in the portage(5) man page for more details)
# required by net-libs/nodejs-bin (argument)
=net-libs/nodejs-bin-6.9.4 ~amd64

Use --autounmask-write to write changes to config files (honoring
CONFIG_PROTECT). Carefully examine the list of proposed changes,
paying special attention to mask or keyword changes that may expose
experimental or unstable packages.

Vamos, con permisos administrativos a /etc/portage/package.keywords/ y abrimos custom como un archivo de texto y ponemos:
=net-libs/nodejs-bin-6.9.4
Guardamos el archivo.
En consola:
emerge --ask --autounmask-write =net-libs/nodejs-bin-6.9.4
Instalar dependencias:
calculate ~ # emerge gnome-base/libgnome-keyring
calculate ~ # git clone https://github.com/brave/browser-laptop

calculate ~ # emerge www-client/brave-bin

Local copy of remote index is up-to-date and will be used.
Calculating dependencies… done!
[ebuild N ~] www-client/brave-bin-0.15.0

The following keyword changes are necessary to proceed:
(see “package.accept_keywords” in the portage(5) man page for more details)
# required by brave-bin (argument)
=www-client/brave-bin-0.15.0 ~amd64

Use --autounmask-write to write changes to config files (honoring
CONFIG_PROTECT). Carefully examine the list of proposed changes,
paying special attention to mask or keyword changes that may expose
experimental or unstable packages.

Vamos, con permisos administrativos a /etc/portage/package.keywords/ y abrimos custom como un archivo de texto y ponemos:
=www-client/brave-bin-0.15.0
Guardamos el archivo.
En consola:
emerge --ask --autounmask-write =www-client/brave-bin-0.15.0

Ya instalado, arrancamos Brave desde consola:
$ brave

Notas: Igual te puede solicitar calculate ~ # emerge x11-themes/clearlooks-phenix
Sino aparece Brave en los reopositorios prueba agregando este overlay:
calculate ~ # layman -a wizard

Instala la versión 0.15.0 en su web está disponible la 0.16.9 release