Is it possible to install the Dell Customized ESXi 6.5 on a T30 with a Intel Xeon E3-1225v5 ?
This is not listed in VMware compatibility list but you can try with dell customized image, if you find issue installing with any unsupported hardware device then you can make changes to bootable image by adding required VIBs.
Try installing on a USB flash disk. Confirm all your NIC,Disk etc are detected and drivers are loaded successfully.