I bought GD-77 for hotspot mode only and I've been playing a month with and reached some issues. I've used V0.3.3 (current firmware downloaded 27.9.2019).
- Hotspot mode started anytime if MMDVMHost runs on x86 platform and in this case HotSpot mode was realy reliable (100%)
- Using Raspoberry PI ZeroW worked almost fine - reliable for 95% in case the RasPi was powered from own power supply
- Using Raspberry PI ZeroW sharing radio battery over DC-DC StepDown converter - reliable for less than 1% - All attempts finished with "Waiting for StarPI..." on display
All tests were done on Raspbian and Debian (in case of x86 platform tests) as well as using current MMDVMhost - I don't using any prepared image for RasPi.