I am currently running gentoo on a small laptop dating back to 2008. This is an i686 computer and I wanted to install x11-misc/barrier. The only problem was that in the ebuild there seems to be only support for ~amd64 since it is the only supported KEYWORD. However, setting in /etc/portage/package.accept_keywords x11-misc/barrier ~amd64 the compilation and installation process was successful. I tried it and seemed to work fine. I also looked at their github page and I saw no compatibility problems with linux 32-bit. So I don't see why ~x86 KEYWORD is not available in the ebuild
x86 keyworded, closing