Hi,
As suggested by Houseboatman + Saft on this forum, I've successfully installed the Thule Rapid system for my IONIQ Plugin last february to drive to the Alps.
You need 3 things:
1) Thule rapid system 754
(the bars foot, assembles easily onto vehicles without pre-existing roof rack attachment points)
Thule Rapid System 754
2) Thule rapid system Kit 1711
(the custom adapter kit for mounting a Thule roof rack system, this one is designed for the Kia K3 + Kia Cerato as specified on the box, but it does fit on the ioniq))
You have to adjust the settings found in the Kit 1711 manual, so that the bars (and your roof box) stand horizontal on the IONIQ curved roof.
And make sure the rubber part fits well on the ioniq roof, see my screenshot.
Kit 141711
3) Thule bars
For example the nice wing bars
Roof rack components and accessories
And as already warned in previous posts : roof racks are still not official for the IONIQ, we do this at our own risks...
Tom