I've heard good things about XCP-ng as well and tried it out at home and proxmox seems much easier to use out of the box. Not saying XCP-ng is bad just that it wasn't as intuitive to me as proxmox was when we were moving away from vmware

And there's also Triton[0] and vanilla SmartOS[1] it's based on

[0] https://github.com/TritonDataCenter/triton

[1] https://docs.smartos.org/