Does supporting a great grandchild qualify as head of household if they meet the criteria otherwise? Do you just show grandchild since great is not an option?

[MinhT]

Yes, having a great-grandchild as a qualifying child, being unmarried and paying for more than half of the costs of keeping up a home would allow to file as Head of Household.

As the great grandchild is a direct descendant of your grandchild, in TurboTax, you can use grandchild as the relationship with you.