Hi,

First, I assume you have 25G capable NICs in the Nutanix nodes?

I think the general rule of thumb is that DAC cables tend to only be supported for interconnecting same vendor kit.  I.e. HPE will only support those Aruba DACs for connecting Aruba switches to other Aruba devices (or at a push possibly to HPE servers). 

Ideally you would use Aruba transceivers in the switch and appropriate transceivers in the NIC (so Intel / Broadcom / Mellanox or whatever the NIC happens to be) and then connect with appropriate cables.  That said, most people will probably use the same optics at both ends (i.e. whatever vendor the switches are).

Will DAC cables work?  Almost certainly (in my customer days we used Cisco Twinax DACs between our Nutanix nodes and Nexus switches).  Will HPE support it if there is a problem?  Almost certainly not as they will only have been tested and certified for use with that vendors equipment.