Creating multiple clusters in different datacenters and replicating one?

I have a request to create multiple clusters in different datacenters and one cluster would be the replica of the other one. Any idea how should I go about it?

There is no perfect solution to this requirement.
The concept of “replica cluster” doesn’t exist.
I suggest to develop good IaaC (for instance, Terraform code) and deploy the “same” cluster using same the basecode.
If you need to have also same applications/volumes on both clusters, you can use your CI/CD pipeline to deploy on both or periodically refresh “clone” cluster using a backup/recovery tool like Velero.

I was hoping someone could give me an introduction to multicluster. The same cluster has a mongodb operator and the developers of the operator are telling me I could use the mongodb on both clusters but I need something like a mesh or multicluster.

This is a completely different matter.
Waiting for other replies…

Probably they want replicas of apps, not k8s cluster itself. You can use argocd for that.