Hello, I fixed the headset play simply adding a 1mm headset spacer (cutting it to a C shape) above the C ring, I think a 0.5mm would be enough but i don't have anyone right now. C-ring I'm using is this one
a had around. Expander I'm using is Deda Expander 70,very stiff and light, those AliExpress expanders with O-rings or springs doesn't convince me. also I'm not using the Hygge handlebar, Og-evkin one instead.
There's no play at all, I filled the tiny gap (smaller than the one at the bottom of the head tube) with grease to avoid dust and water ingress. Expander is tighten to the Deda's recommended 5Nm and stem bolts also 5Nm.