I just followed the installation instructions here https://archlinuxarm.org/platforms/armv8/broadcom/raspberry-pi-4
It starts the boot up process and looks good until 6 seconds in after evaluating the USB devices. I see looping of these 2 messages:
mmc1: unrecognized SCR structure version 4
mmc1: error -22 whilst initialising SD card
I've tried 2 different microSD card in the RPI 4 B (4GB)