For k3s you have to add an extra option to the cadviser container args so that it can find the countainerd socket.
kubectl -n checkmk-monitoring edit daemonsets.apps checkmk-node-collector-container-metrics
...
containers:
- args:
...
- --storage_duration=1m0s
- --containerd=/run/k3s/containerd/containerd.sock
last line is the one to add