Lock Down 410c "Boot Menu"

Hey Folks,

I am currently trying to secure my qualcomm dragonboard 410c with Windows IOT Core. When i boot the Device i get into the startmenu of the board by pressing +,- & Power. (Not the Windows one but it seems from the board itself. Does anyone know how to disable or lock this with a password?

According to Microsoft i need a closed firmware on my board, but I haven’t found anything on the support pages

https://social.msdn.microsoft.com/Forums/en-US/682865ec-1806-4155-868a-c5d55e7b8e09/lock-down-qualcomm-quotboot-menuquot?forum=WindowsIoT