TeX Live manual installation
Gentoo provides packages for TeX Live in the official tree, but they are very difficult to update. The TeX Live packages in the tree are several months (sometimes a year) behind upstream, while users who install TeX Live manually with the tlmgr manager get updates every day.
This procedure is very similar to other package managers like pip in python or the package managers of GNU R (using cran), and Perl (using cpan).
This page collects user experience and hints about the manual installation
Get the latest installer from https://www.tug.org/texlive/ and follow the instructions to install to /usr/local.
The manual TeX Live installation provides many packages, which could be installed via Portage too. To prevent Portage to install app-text/texlive as dependency, one can add the package names in a .provided file:
app-text/texlive-9999 app-text/texlive-core-9999 dev-texlive/texlive-basic-9999 dev-tex/revtex-9999 dev-tex/tex4ht-999999999999 dev-tex/latexdiff-9999 dev-texlive/texlive-fontsextra-9999 dev-texlive/texlive-fontsrecommended-9999 dev-texlive/texlive-fontutils-9999
9999 tells portage, that we provide already the latest version of the package via tlmgr.
tlmgr update --all
The manual installation of TeX Live bears the chance of other conflicts and bugs than a Portage installed TeX Live. Keep track of all commands regarding the administration of TeX. Using the package manager of the distribution and of a software suite on the same system is always a challenge.