Recently I've ordered new RPi4 B to replace one of my very-very first RPi's, but suddenly I found that it won't boot 64-bit version of ArchLinuxARM.
Small investigation shows that it's a new revision of the board, named "1.5" in firmware (e.g. /sys/firmware/devicetree/base/model), and marked as C0T on chip.

This revision requires changes in FDT before Linux kernel boot, to sync it up with device firmware, I've found some reports, but the only working solution was from guys in NixOS, who updated their U-Boot and applied an additional patch for FDT patching.

ArchLinuxARM didn't do any of that yet, so I've prepared a patched u-boot PKGBUILD as a temporary workaround: https://github.com/rayslava/rpi4-C0T-uboot