The official release of Alpine 3.9.3 for armhf is missing the kernel and initrd for the original Raspberry Pi model B.

Config.txt correctly lists:

[pi1]
kernel=boot/vmlinuz-rpi
initramfs boot/initramfs-rpi

But all the required files are missing from boot/.

(from redmine: issue id 10407, created on 2019-05-07)