To migrate a VM from a Nutanix vSphere cluster to AHV, the valid methods are using Nutanix Move and Cross-Hypervisor DR. Nutanix Move is a robust tool designed for the seamless migration of workloads to AHV, while Cross-Hypervisor DR allows for disaster recovery across different hypervisors, which can facilitate the migration process. Storage vMotion and Live Migration are not suitable for this scenario as they pertain to VMware environments and do not support cross-hypervisor migrations specifically involving Nutanix AHV.