K8s and Proxmox operate at different levels. You can run k8s on Proxmox, and that’s what I’ve been (very slowly) building up to at home.
With Proxmox you can failover VMs between nodes as long as storage (including VM boot disk) is external to the nodes. This can be NFS on a NAS, iSCSI, Ceph or many other options.
It’s even possible to failover a USB device (e.g. a Zigbee controller or similar) by attaching one on each node and mapping them using Resource Mappings (search on the announcement post: proxmox.com/…/proxmox-virtual-environment-8-0).
This can also be used if you’re deploying k8s on top of Proxmox just as well.