Let me try to clarify:
I can create the cluster in air gap:
kubectl get no
NAME STATUS ROLES AGE VERSION
ipc-z8g4-i3-ubuntu Ready control-plane,etcd,master 7m6s v1.21.1+k3s1
wfc-barak2-ubuntu Ready control-plane,etcd,master 7m34s v1.21.1+k3s1
wfc-z8g4-22-ubuntu Ready control-plane,etcd,master 7m20s v1.21.1+k3s1
When I check the kube-system pods, some of them fail:
kubectl get po -n kube-system
NAME READY STATUS RESTARTS AGE
coredns-7448499f4d-6gn8v 0/1 CrashLoopBackOff 6 8m1s
helm-install-traefik-crd-4866r 0/1 Completed 0 8m2s
helm-install-traefik-tvxtt 0/1 Completed 1 8m2s
local-path-provisioner-5ff76fc89d-wp65x 1/1 Running 0 8m1s
metrics-server-86cbb8457f-7m4zm 1/1 Running 0 8m1s
svclb-traefik-57cpj 2/2 Running 0 7m12s
svclb-traefik-lqhc2 0/2 ContainerCreating 0 7m12s
svclb-traefik-qtzmt 0/2 ContainerCreating 0 7m12s
traefik-97b44b794-4jxdc 0/1 ContainerCreating 0 7m12s
Checking the pods, it seems they are looking for rancher/pause:3.1
kubectl describe pod/coredns-7448499f4d-6gn8v -n kube-system