Hello,
There are some examples in bare metal in the SDK available, but there is no way to use the Bluetooth LE application without the OS Abstraction layer due to the dependencies in the libraries and stack management.
I would recommend you to check the Bluetooth LE Application Developer's Guide for a deeper understanding of how it’s the stack working and which are the necessary elements to have it working, you can find the document in the SDK documentation, I would recommend you to check especially the chapter 9.5 RTOS as we do not have those examples without RTOS.
Sorry for the inconveniences this might cause you.
Regards,
Estephania