can I share the same datastore between different VMware 6.5 clusters?

Is it possible to share the same datastore between multiple VMware clusters of the same version (both 6.5 or both 6.7)?

It is the norm to share the datastore between multiple hosts in the same cluster (and it is required for vSphere HA), but I'm talking about multiple, otherwise independent clusters each one with its own nodes and vCenter.

By "sharing" I mean having both clusters actively working on the datastore with virtual machines and possibly the datastore heartbeat for HA. The individual VMs will be in only one cluster inventory, but on the same datastore there could be a mix of VMs from the two (or possibly more?) clusters.

My question is deliberately generic, but if you need a concrete example think about two Essential Plus clusters, three nodes in each cluster, all of them connected via iSCSI to the same LUNs. Reason for the question is to avoid hard splitting the available SAN space in two parts, one for each cluster, without being able to "rebalance" storage if one LUN/datastore gets full white the other still has available space.

It should work, technically. Even with ESXi 5.5, it would have worked. However, I would separate different LUNs per different clusters. https://communities.vmware.com/thread/341938 For your case, I think it would be easier to create NFS share and expose to both clusters. A simple example: https://www.vmwareblog.org/building-freebsd-file-server/