VMware offers a free version of ESXi 7.0 with limitations (max 8 vCPUs per VM, no vCenter, no backup APIs).

A concise guide to obtaining a portable ESXi 7.0 ISO image and options for running or transporting it.

Once you have the ISO, you can make it "portable" by creating a bootable USB flash drive. This allows you to install or run the installer on any compatible server hardware.

It still supports some hardware that was deprecated in version 8.