FlorianAfter having it just lying around, I finally took the time to set up my Raspi again. I've now got a booting Pi and my first alpine contribution (https://gitlab.alpinelinux.org/alpine/mkinitfs/-/merge_requests/215) 
(the `usbdelay` command line parameter of alpine's initramfs `init`semms to get ignored in some cases - which is kind of an issue, if your root filesystem resides on an external USB HDD that takes some 20seconds to become available)
