Please confirm which NUC model supports ESXi5.x/6.x from below list -
Thank you for your interest on our latest NUCs with 6th gen processors; however, the feature that you are requesting requires Server Platform. NUCs support Windows® 10 (64-bit), Windows 8.1* (64-bit) and Windows 7* (64-bit).
More details at Intel® NUC — Supported Operating Systems
The ESXi Hardware requirements are the following:
vSphere 6.0 Documentation Center
WMware® provides this tool to find compatible systems.
VMware Compatibility Guide: System Search