These are just personal notes, please ignore this page.
- Make sure all this is in accordance with best practices.
- What should users be warned about, 3rd party installation method wise ?
- What about a tarball with binary ? Thinking Google Earth or the like.
- What about .rpm, .deb ? Just say no ?
- What about ".sh" installers ? Thinking  or .
- What about "app stores" ? I know that some say wiki page, for example, is a real no no. What about others (Guix, )
- Suggest chroot/
- things like PREFIX ?
The Gentoo repository is a trove of easily installable, stable, free software - one of the largest in the world in fact.
Third party, or even user-written software is sometimes needed though, and Gentoo provides facilities to compile, install, and manage user custom packages.
Software on Gentoo is compiled, installed, and managed through Portage - a modern, advanced, package build, management and distribution system. Portage installs files to the root partition (though it is possible to install elsewhere). These files are tracked, to allow updates and uninstallation. This article covers what can be done to install third party software on Gentoo, notably using Portage.
Caution should be taken concerning the safety and security when considering software from outside the Gentoo repository. The provenance of software should also be considered. Never install or run untrustworthy software. Data loss and theft is a real possibility.
This article does not cover usual software installation on Gentoo, see the Handbook on installing software with Portage from the Gentoo repository.
The easiest way to install software not currently present in the Gentoo repository is to use a third party repository if someone has already made an Ebuild for the required software. Just add a repository then use Portage to emerge as usual.
See Eselect/Repository#Usage for details.
Installing software from source
Software should not be installed to root ("/") other than through Portage. Never type "sudo make install" or equivalent, this will clutter root with files that cannot be tracked and could event corrupt the Gentoo installation. "make install --prefix=~/.local" or such may be used, though it is recommended to write an Ebuild.
Using Portage is the recommended way to install all software system-wide on Gentoo. Portage will track all files installed to the root partition, as to allow clean removal and updates - as well as management with the system administration tools.
On a default installation, Portage will search for software in the Gentoo repository. Given, say a .tar.gz containing C source code, it is possible to write a custom Ebuild that will instruct Portage how to compile and install the package.
Docker is available on Gentoo and may be helpful for some software that is not available fin the repository.
vm's plugin managers