FWIW The Migration tool doesn't seem to work for me for warm migrations for standalone (single dell server) Esxi 6.5 to standalone XCP-ng 8.3 and the latest XOCE. The account of migration of 3 servers is a follows;

Guest 1 - snapshot, ran the XOCE migration, waited 4 hours observing the disk copy progress, then nothing. no final snapshot, no task completion. Started again as a cold migration completed and then had to rename VM and disks from delta labels given during migration.

Guest 2 - snapshot ran cold migration and on completion then had to rename VM and disks from delta labels given during migration.

Guest 3 - snapshot ran cold snapshot ran cold migration, one disk completed, second disk didn't with task destroyed due to exceeding the 24 hour task limit (assumption).

The 24 task limit is a bit annoying, but I have made the config change to give it another go this weekend.

The tool made the migration less fiddly but the issue with the warm migration make it a higher touch experience.