Of course you can run ESXi on Mac _hardware_. You can run nearly any OS or software on the Mac _hardware_. It's, until recently, pretty standard Intel x86 hardware.

You cannot, however, run macOS on Dell hardware as an ESXi guest. It very clearly violates Apple's EULA for macOS, even if you could trick it into doing so.

You can look around the internet for how to install a macOS guest on non Apple hardware running ESXi. It's not easy, and requires patching ESXi, and more.

Plus, the hosting company you linked to is clearly running things on Mac hardware. They even say it.

Doing otherwise would clearly violate Apple's EULA, which is what all this was originally about.