I got this error as well. Based on this message:
[preflight] If you know what you are doing, you can skip pre-flight checks with `--skip-preflight-checks`
I decided I knew what I was doing and ran:
# kubeadm init --skip-preflight-checks
Not sure if everything is working yet, but that error is resolved.
How's your cluster going? I too am looking at building out a small cluster with tinkerboards.