anti-apXos
If you want automatic kernel updates on antix, you could switch to using the Debian stable-security kernels with the metapackages Debian provides. The package names for those are just linux-image-amd64 and linux-headers-amd64 or similar, with no version number in the package name. These metapackages will always keep the latest Debian kernel installed. Older kernels can then also be uninstalled using apt autoremove (I think the two most recent kernels are kept not just one).
Debian kernels are built with slightly different options than antix kernels, but they work fine for most cases.
If you just want a GUI for doing updates, there’s synaptic.
I’m not sure exactly what you’re unclear about concerning grub updates. If you mean remaking the grub menu config (/boot/grub/grub.cfg) after a kernel update so that the new kernel is on the list, that is done automatically. If you mean reinstalling the grub bootloader itself after an update of the grub packages, then that is not done automatically, either on antix, debian, or any other distro I know of.
On stable Debian/antix, GRUB package updates are very rare, though. There’s never been one for Bookworm (Debian 12, antix-23), for example.
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