Raspberry Pi's have a blob. That blob is only 32 bit and maintained by Broadcom and the foundation.
If you want to use the Raspberry Pi 3 properly now, you need ArchLinuxARM-rpi-2-latest.tar.gz that works very well on Raspberry Pi 2 and Raspberry Pi 3 and is 32 bit.
On the page:
https://archlinuxarm.org/platforms/armv ... berry-pi-3"AArch64 Installation
This provides an installation using the mainline kernel and U-Boot. There is no support for the vendor-provided libraries, extensions, or related software. Some of the hardware on the board may not work, or it may perform poorly."
ArchLinuxARM-rpi-3-latest.tar.gz
IMHO stuff will work fine on 64 bit if:
-a 64 bit blob is provided
-the source for the blob is released as free software and modified and compiled for 64 bit
-completely free software drivers are made and a very small blob only boots the kernel (no config.txt)
Eric Anholt is working on the free software video driver, and the blob runs it's code on the video card VC4 so this may be what is needed.