The various linux kernel packages have not been updated since 2020-08-09. The main Arch Linux amd64 packages are already at kernel 5.8.5.
Looks like there's an issue with the kernel 5.8.x build, as the vmlinux.kpart file for 5.8.0-1 aarch64 chromebook does not boot. A script I have to build vmlinux.kpart files produces a bootable 5.7.8 vmlinux.kpart using the Image file included with that kernel package, but will not build a bootable 5.8.0 vmlinux.kpart from its Image file. I did have to expand my Kernel partition to 48 MB in order to completely contain the 5.8.0 vmlinux.kpart, but that did not help bootability. 5.7.8 boots fine from the 48 MB Kernel partition for both the distributed linux-aarch64-chromebook vmlinux.kpart and the one I custom built.