I’d expected this but it still sucks.
XCP-ng or Proxmox if you need a bare metal hypervisor. Both open source, powerful, mature, and have large communities with lots of helpful documentation.
I think you can migrate ESXi VMs directly to XCP-ng. I have moved onto it about 6 months ago and it has been solid. Steep learning curve, but really great once you get the hang of it, and enterprise grade if you need stuff like HA clustering and complex virtual networking solutions.
I managed to migrate all mine to libvirt when I dumped esxi. They dropped support for the old opteron I was running at the time, so I couldn’t upgrade to v7. Welp, Fedora Server does just as well and I’ve been moving the VM hosted services into containers anyway.
Ofc… well, we’ll see what IBM does with RedHat. Probably something like this eventually. They simply can’t help themselves.