With Gentoo I believe it is more fun, because of all the options gentoo provides out of a box. More kernels, more work to do.
ls /var/db/repos/gentoo/sys-kernel/
asahi-sources/ git-sources/ linux-next/ scx-loader/
bliss-initramfs/ gnumach/ metadata.xml udev-hid-bpf/
cryptodev/ hurd/ mips-sources/ ugrd/
dkms/ installkernel/ modprobed-db/ vanilla-kernel/
dracut/ kci-dev/ pf-sources/ vanilla-sources/
dracut-crypt-ssh/ kergen/ raspberrypi-image/ virtme-ng/
genkernel/ kpatch/ raspberrypi-sources/ zen-sources/
gentoo-kernel/ linux-docs/ rt-sources/
gentoo-kernel-bin/ linux-firmware/ rumpkernel/
gentoo-sources/ linux-headers/ scx/
Not all these directories are different kernel packages, but anything with -kernel or -sources at the end is.I believe at this writing only Linux and HURD are officially supported standalone. Which IMHO is sad because Gentoo kFreeBSD was really cool but oh well. There is still the Gentoo prefix project, though even there support for the BSDs is iffy:(
If you're running on a different platform then perhaps you need the raspberrypi or asahi kernel