There are three options worth very seriously considering.

XCP-NG (formerly Xen, based on what used to be the Citrix codebase) is a mature, stable and enterprise ready platform. It comes with some costs for an enterprise level deployment, but it’s definitely worth comparing against VMware as the potential savings could be substantial.

Then you have KVM (Kernel Virtual Machine), developed by Red Hat. Unlike XCP-NG, this comes at absolutely no cost, and in fact you almost certainly already have it installed, as the core technology is part of the Linux kernel. KVM is powerful, open source and free hypervisor that can absolutely handle enterprise workloads. Oracle uses it for their entire cloud platform, and Amazon still uses it for a substantial amount of AWS if I recall correctly. With that said, while the hypervisor is incredibly solid, the management tools vary a little. Basically, expect to do a lot more from the command line.

The solution to that problem is Proxmox. This is a prebuilt Linux OS based on Debian, but carefully fine tuned to support KVM with a custom web interface to handle cluster management, as well as having fantastic support for advanced storage technologies like Ceph and ZFS. Proxmox also takes full advantage of the ability to run both virtual machines and LXC containers on the same platform, giving you great lightweight solutions for deploying Linux machines. There’s some cost for enterprise use, but it’s very low compared to other enterprise virtualization options.