Background:
Looking to build images on my amd64 system for my aarch64 raspberry pi systems.

Info:
OS: Kubuntu 19.10
Docker version 19.03.2, build 6a30dfca03
Installed buildx by downloading linux-amd64 release and plopping at ~/.docker/cli-plugins/buildx.
Set "experimental": "enabled" in ~/.docker/config.json

Example repro command:
~$ docker buildx ls

ERRO[0000] failure getting variant error="getCPUInfo for pattern: Cpu architecture: not found"
NAME/NODE DRIVER/ENDPOINT STATUS PLATFORMS
default * docker
default default running linux/amd64, linux/386

In a preliminary check, it looks like buildx is looking for a label "Cpu architecture" in /proc/cpuinfo? This label does not in /proc/cpuinfo on my system, which is effectively stock.
cat /proc/cpuinfo | grep -i "architecture" | wc -l => 0

It seems as this is only a cosmetic error, commands seem to execute just fine. Seeing as how it later detects "linux/amd64", somewhere else it is clearly able to get amd64.