When I used Gentoo the normal was to install gentoo-sources, which gives you the kernel source code but doesn't compile it. You then have to compile and install

When I used Gentoo the normal was to install gentoo-sources, which gives you the kernel source code but doesn't compile it. You then have to compile and install the kernel yourself without any support from the package manager. If you're running on a different platform then perhaps you need the raspberrypi or asahi kernel