This article will show you how to change the WiFi channel used by the Hamilton Conversion Kit for Hotspot purchases to 2.4 GHz from 5.0 GHz
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This relates to the outbound hotspot from the device.
Open Settings > Wifi > Hotspot Connection
Click "WiFi Hotspot" > Select "AP Band" > Select "2.4 GHz"
You do not need to use the Hotspot to connect CarPlay but this is an optional step in the background to minimize any potential interference between a hotspot search and CarPlay.
Your device cannot simultaneously be connected to CarPlay and to another device as a hotspot. The only use case for the hotspot outbound functionality would be if you had a 4G T-Mobile SIM in the Hamilton device and wanted to allow a passenger to connect to the device as a 4G Hotspot (e.g. for a kid's iPad in the backseat).