I have a rather general question, what would be the easiest way to clone a rancher-provionned cluster? To migrate it to all new-nodes without any relation to the old cluster (and without taking into consideration data recovery) ?

if you are not changing distribution then perhaps just add new nodes to that cluster and then delete old nodes

The issue is currently, my cluster is relying on a custom system from my hosting provider for the node to communicate between themselves via a sort of private network - my new cluster is on another provider and doesn't have that. So immediately i can't add new nodes form another provider to my existing cluster.