DAHUA NVR - Shutdown from UPS

I am planning to install a Dahua NVR on a remote place (game-farm) in South Africa with an unstable main power. A 3KVA UPS will be dimensioned for 12 hours supply for about 750W continuous load, remaining 50% of battery capacity to avoid deep discharge (1 large PTZ, 14 cameras, linked to an alarm system, GSM and secured internet access for remote control).

How can I configure a DAHUA NVR to shut-down when UPS battery is low?

I am an IT professional and usually configure such functionality for Linux/Windows enterprise servers with a local monitoring client listening on a secure and firewalled port for a login followed by a shutdown command, or a client listing to UPS sending "remaining time left" messages (also on a secure SSL/SSH port), and then the device itself will decide when it is time to shut down.

Is there any supported and proper ways to do this on Dahua NVR's? I try to stay away from hacks and really want to use a method supported by all the major UPS brands like APS/Eaton etc.

I read the DAHUA manual stating "Always use the stable current, if necessary UPS is a best alternative measure", - that funny Chinese made me smile.

For sure it must be a way to shut down the NVR properly in order to avoid a severe data loss?

Or perhaps DAHAU is not the "right" brand for more "demanding" and professional use?

Any information and help is highly appreciated,¨

Thanks!