How can I make a radar chart with polygons instead of circles in amCharts5?

In amCharts 4 you could make a radar with polygons:

https://www.amcharts.com/docs/v4/chart-types/radar-chart/#Circular_vs_linear_grid

I did not find this option in amCharts 5. Here is a demo of a radar chart with circles in amCharts 5:

https://www.amcharts.com/demos/radar-chart/

Does the option for polygons no longer exist, or does anyone know how it is done?