There are articles on this topic, but I have decided to summarise everything in one, according to the tools we have in 2019 for the job. Provided you have the means mentioned, the task should take you up to 5 hours or less to get running again. It required however around 5 days for me to get there.
HOW TO: BOOT VMware vSphere Hypervisor 7.0 (ESXi 7.0 ARM) from an iSCSI LUN for the Raspberry Pi 4, Step by Step Tutorial with screenshots. Setting up the Synology SAN to allow the Raspberry Pi 4 to BOOT ESXi 7.0 ARM edition.
HOW TO: Install and Configure VMware vSphere Hypervisor 7.0 ARM Edition (ESXi 7.0 ARM edition) on a Raspberry Pi 4, Step by Step Tutorial with screenshots. From Download, Checking Media, to Completed Hypervisor Installation. Please check the requirements list before installation.
The Raspberry Pi Foundation works to put the power of digital making into the hands of people all over the world, so they are capable of understanding and shaping our increasingly digital world, able to solve the problems that matter to them, and equipped for the jobs of the future.
We provide low-cost, high-performance computers that people use to learn, solve problems and have fun. We provide outreach and education to help more people access computing and digital making. We develop free resources to help people learn about computing and how to make things with computers, and train educators who can guide other people to learn.