Some updates:
I followed the instructions posted by @Pudge here:
I have succeeded in installing the base system on a SD card and also replaced the Arch kernel with the one from RPi foundation. All is well, the system boots up and I can log in as root or the alarm user.
Next step would be to clone the system into the SSD.
I need to go out for some “real life” errands. When I get back, I’ll go ahead with the rest of the instructions. Will keep you posted.