Yes, you can do this with ceph on commodity hardware (or even your compute nodes, if you are brave), or if you have a bit of cash, something like a netapp to do NFS/iSCSI/NVME-oF
Use any of these with the built in HA manager in proxmox
Ceph RBD can technically support multi-writer access through exclusive locking, but it won't be the same as multi-writer.
You can set up a radosgw outside of the proxmox and use objects.
But ceph is fundamentally a distributed object store, shared LUNs with block level multi-writer is fundamentally a tightly coupled solution.
If you have a legacy need that has OCFS or a quorum drive, the underlying tools proxmox is an abstraction can sometimes be used as these types of systems tend to be pets.
But if you were just using multi-writer because it was there, there are alternatives that are typically more robust under the shared nothing model like Ceph uses.
From what I read about VMFS yes ceph allows you to have a shared block devices (RBD = rados block devices) across a cluster, and proxmox VE HA makes sure only one instance of the VM is active on the cluster to avoid having multiple writers to the same disk image.
Use any of these with the built in HA manager in proxmox