A few days ago, I bought Atom C3758 based Mother Board.
Unfortunately, ESXi 6.5/6.7 have no inbox driver for X553 GbE.
So I build x553 only driver from ixgbe-5.3.6 linux driver.
I'm using it with following parts.
Asrock Rack C3758D4I-4L
Kingston KVR24R17D4K4/128
Intel ET Dual Port Server Adapter
(initial connection by igb inbox driver)
Transcend JetFlash 720S
SilverStone SST-CS280 / SST-ST45SF
I have tested with IPv4, MTU9000, no VLAN only. (mainly iSCSI connections)
Other setting may cause problems.
However, if you are interested in the driver, try it.
To use this driver:
# esxcli software acceptance set --level=CommunitySupported
# esxcli software vib install -v /tmp/net65-x553-5.3.6.x86_64.vib