As you have possibly noticed, VMWare was bought by Broadcom. This has a huge impact on the VMWare customers, there are massive changes now in progress, like no free ESXI and no perpetual licences any more.
Some customers where lucky to extend their contracts in time to the known conditions so that they have now time to think what to do, some have been not so lucky and face now massive price changes (its reported that some customers where shocked by 1200% increasement!)
Of course this is for most VMWare customers unacceptable and business critical, so the question arises: are there alternatives? Maybe ones that will not put you in the same position again in a few years?
The short answer is: yes there are!
Naturally, there must be a transition period when switching to a new solution, and the concepts you used till now with VMWare must be reevaluated and adapted.
The two most named alternatives in the OpenSource world are Openstack and Proxmox VE.
Openstack has a quite different approach then VMWare, it focuses on simple fresh deployment and drop of VMs for real huge environments, not so much on the easy manageability for VMs for administrators and High Availability for VMs, and its known for its complexity.
Proxmox VE on the other hand focuses on the same things VMWare does. Its an complete free and OpenSource solution, but you can get enterprise level support if needed.
It uses the KVM technology which is fully integrated in the Linux kernel and turns every Linux host in a powerful hypervisor.
Proxmox VE uses then several KVM hypervisors as nodes to build a cluster and puts a very sophisticated management layer on top of the cluster that handles the deployment, behaviour, storage, network and more of your virtual machines.
This management layer is accessible via Webinterface, but also via commandline tools. It gives you very advanced features that are similar to VMWares feature list, like load based rebalancing of VMs, High Availability for VMs, HA groups which allow you to determine on which specific nodes a VM can start (important for some licence types for software that runs inside of VMs), Software defined networking and much more.
It also allows you to manage LXC based containers in the Proxmox VE cluster which can be much more resource saving then using VMs.
Yes, there is no 1 to 1 feature comparison list between Proxmox VE and VMWare. But you can do everything that you have done in VMWare also in Proxmox VE.
The scalability of a Proxmox VE cluster is also impressive: Usual deployments show a size of up to 32 nodes, but this is not a hard limit. If you need a bigger Proxmox VE cluster, its possible, but it depends on your network latency. Production clusters up to 100 nodes with 16.000 VMs have been already reported.
Automated deployment of VM groups via Ansible or Terraform is also an example for the flexibility of Proxmox VE.
Finally, there is the old problem with VM backups, it can be really painful to create and manage consistent backups of VMs.
Proxmox offers here the Proxmox Backup Server, a fully integrated OpenSource solution for Proxmox VE that manages incremental, fully deduplicated backups (backup and restore process), including integrity check and encryption for VMs, physical hosts and containers.
Proxmox VE is not a new solution on the market, it has been around since years and has proofed itself as an enterprise ready, rock solid solution. The development speed of Proxmox VE is steady, every few month new features are introduced, the community around Proxmox is very active. And with the changes that VMWare introduced now it will be the number one alternative to go for customers that want to escape the high price vendor lock in from VMWare.