Thingspeak in an x86 Docker environment is already supported, but I struggled to find anything similar for ARM.
So, I adapted the x86 install, replacing the required base images with two available for ARM architecture on Docker hub (https://hub.docker.com/). It was also necessary to add ruby on rails to the install. The resulting Docker build scripts are here: https://github.com/nicbkw/docker.thingspeak
Be aware that the install takes around 30 minutes due to the need to build and compile some components from source for the ARM platform.