Kiali's mesh page shows you which namespaces are being managed by each controlplane. Using this can be helpful during a migration from 2.6 --> 3.0. We should publish a blog post describing how to do this.

draft here: https://docs.google.com/document/d/1i0291ZRme-5y37vrcsdLaIaIFGOk7CBjmTOKV_O5JHQ/edit?usp=sharing