Overlays

The default Gentoo repository may not have the desired package. However, more packages exist in external repositories.

Instructions

Look for the desired package (eg.: foo/bar) in https://gpo.zugaina.org/.
Make note of the repository (eg.: example).
Find the relevant repository with eselect repository list.
Select the repository with eselect repository enable example.
Synchronize the repository with emaint sync -r example.
Check if the package exists with emerge -s foo/bar.
Mask all external packages with */*::example in package.mask.
Unmask the specific package with foo/bar::example in package.unmask.
Check if the package needs any additional configuration with emerge --ask ... foo/bar.
Update configuration manually or with dispatch-conf.
Emerge the package.