Input_datetime helper issues

HI Guys,

I have been trying to figure out how to get this to work but can’t seem to wrap my head around it so I hope somebody can help out.

With the recent changes in the IFTT subscriptions I have to cut down on some applets. I am running the android companion app which conveniently sends the “next alarm” over to home assistant. So far so good but I need to be able to use that time for automations.

I have created an input_datetime helper through the front-end, when I can get that “next alarm” time mapped to that input (which should be possible through “input_datetime.set_datetime”) I am able to use that device as a trigger for an automation.

This is how the next_alarm is represented in home assistant:

Please note that the state represents the UTC time, I am looking for the local time, which I can derive (in the purest form) from the Time in Milliseconds attribute by using:

{{ (state_attr('sensor.bram_s10e_next_alarm', 'Time in Milliseconds')/1000) | timestamp_local }}

The resultt of the above, according to the template designer is valid:
2020-09-28 06:00:00

I have tried every possible notiation I could think of to inject the template result in the input_datetime.set_datetime service without any luck so I hope one of you guys is able to help.