nRF9151 use sys_poweroff()

Question

I am working on a project with the nRF9151 chip. In this chip, I am using the LTE modem in eDRX mode . 
 Apart from eDRX mode , I also want to put the MCU into sleep mode . 
 I have tried several approaches:

The simplest option – using k_sleep(); .

The second option – using pm_device_action_run(dev, PM_DEVICE_ACTION_TURN_OFF); 
 
 Here, dev refers to any peripheral device. 
 However, I couldn't figure out how to put the entire processor into sleep mode. Is this possible?

The third option – I tried using the pm_state_force() function, but it is not available for this processor. 
 
 The error I get is:
 
 bash

# CONFIG_PM was assigned the value y, but got the value n. Missing dependencies:
# SOC_SERIES_EFR32BG22 || SOC_SERIES_EFR32BG27 || SOC_SERIES_EFR32MG24 || (SOC_SERIES_DA1469X && SOC_FAMILY_RENESAS_SMARTBOND) || (SYS_CLOCK_EXISTS && HAS_PM)

In both the first and second approaches, I did not see any difference in current consumption . To measure power consumption, I am using PPK2 (Power Profiler Kit 2) . 
 I found a reference in the documentation mentioning the sys_poweroff() function. Using this function reduced power consumption . 
 However, I encountered issues with waking up from this mode . To exit power-off mode, I use a GPIO interrupt , which works fine. 
 However, I want to use the RTC timer . I tried setting up an RTC-based interrupt, but it does not trigger from power-off mode . 
 I haven't found an example of how to correctly use this function on this processor. Do you have any information or an example of how to use it properly?