kubectl proxy unauthorized when accessing from another machine

The --accept-hosts access control is for checking of the hostname, so it won't start with a / (slash). You need to do:

kubectl proxy --address 0.0.0.0 --accept-hosts '.*'

(Make sure you shell escape the .* as it may match files in the current directory!)

More information at: https://kubernetes.io/docs/user-guide/kubectl/kubectl_proxy/