Buttonless DFU + FreeRTOS Example?

I'm struggling to get buttonless DFU to work with FreeRTOS.  I've gotten buttonless DFU sample to run on the hardware.  I also have FreeRTOS running on the hardware. However when I try to put them together, I'm needing to make choices about RTC1_IRQHandler and configTICK_SOURCE == FREERTOS_USE_SYSTICK and NRF_SDH_DISPATCH_MODEL... it's a lot of confusing acronyms. I'm starting to learn the internals of how all this works...

Is there a guide of how to add Buttonless DFU to a FreeRTOS application?  Or to add FreeRTOS to a buttonless one?

The issue I'm facing is a runtime issue -- the service is there, and the nRFT Toolbox iOS app will connect. But the device never switches to DFU mode.

we use a realtime clock, s140 soft device (7.0.1).  No bonds. Have the latest SEGGER Embedded Studio and nRF5_SDK_16.0.0