There is a Migration path directly from XO for ESXi VMs to XCP-NG. It's currently bugged if you use the latest "Release" version of 8.2.1 for XCP-NG and it's supposedly fixed in the 8.3-B2 release of XCP-NG. I'm going to be playing with an upgrade of my testbench to 8.3-B2 and try another set...