By starting the HEQ app, pressing the H12 button. Leave the H12 app be, and then start (I assume any) ground control Software connecting by UDP: Yes. It is a hack. Not pretty. But it works. But also sadly only for a short while.
After 30 minutes the interface enabled by the H12 app shuts down. Now obviously… The GCS can be disconnected, the H12 app then closed and started again. In the middle of a mission, mind you. But yes, then you may connect once more and get the next 30 minutes.
I am testing the H12 for use in a boat. Then 30 minutes fly time is not raising any eyebrows, we run missions that may last for hours. 30 minutes working time further seems to be a consistent behaviour based on my and others experience. My suspision is that this behaviour may be as intended by the HEQ H12 app developer.
Disabled battery optimization. Allowed unlimited background threads. It makes no difference. Any suggestion for other possible mitigation that extend the fly time would be highly appreciated.