LACP on stacked HP 2920-48G

Sounds like you're almost there.

You'll need to create a "team" on the server using two or more of the Intel ports. Use the Configure option in the NIC settings to choose 802.3ad.

Let's say you're using a team with two server NIC ports into two ports (47 and 48) on the same switch.

On the HP switch,

HP Procurve 2920> config
HP Procurve 2920(config)# int 47-48 lacp active
HP Procurve 2920(config)# show lacp

Check to be sure lacp status is "success"

Now patch in your server, each Intel NIC port to an HP port. Come back to the CLI and

HP Procurve 2920(config)# show lacp

to check if it's successful. Look for LACP partner = yes on both interfaces 47 and 48 and be sure all interfaces in your team are "up" Check your server to be sure traffic is flowing through both NIC ports. If so,

HP Procurve 2920(config)# write mem

to save configuration to memory.

802.1x was specifically designed for end-point devices to authenticate to network switches and was not designed for switch-to-switch connections. Because of this, it is highly unlikely that you will find any switches that can be a 802.1x client, so the answer to your Y question is no.

To answer your X concern (see XY problem)- preventing a malicious entity from monitoring and intercepting traffic can only be reasonably accomplished by maintaining physical security of your network hardware and cabling infrastructure. As @Ron mentioned, it is trivial to configure a device to act as a network tap that can be placed between any one of your switches -provided that physical access can be attained- that can then passively monitor traffic on your network, regardless of whether you have 802.1x configured. MACSEC would be an example of a technical measure that could potentially prevent this type of attack.