Driver sr need updating gentoo
If you want to stick to ebuilds, yet automatically configure your kernels, I suggest looking at https://github.com/jollheef/jollheef-overlay/blob/3a59396be2cbbdb1202e30ac577c3676fa5d9a85/sys-kernel/linux/linux-4.17.4.ebuild for inspiration.
Downloading, compiling, and installing the kernel is trivial: you (roughly) do .
Kernel configuration is the most challenging part of running your own kernel.
Depending on how far you want to deviate from the defaults, it can take you up to several hours to manually configure a kernel.
This is too time-consuming to do on the 486 PC so I use a modern machine to do the compilation then move the disk over to the ancient PC. I heavily reference official Gentoo Wiki x86 handbook with some tweaks to suit the 486 as well as ease of repeated builds.Software like systemd requires certain kernel features to work properly.