Help with Bluetooth LE stack

Hello,

I would like to ask for a bit of help. I'm absolutely not familiar with 
bluetooth, and one of my components for my project is a bluetooth LE 
device[1], and I'm having some troubles with the BT stack.

Initially I've based my code on the FreeBSD-BLE[2] examples, and my 
stack worked. However, there was a power outage and the device 
restarted, and this example stuff is still getting data, but my stack is 
not anymore. What so far I have (and used to work but doesn't anymore) 
is at [3].

I've tried reading through the manuals and docs, but it's absolutely 
blurry. Like NG_HCI(4) tells me to do 3 things during HCI init 
(Read_BD_ADDR, Read_Local_Supported_Features, Read_Buffer_Size) but 
doesn't exactly tells me how. I'm using the bluetooth(4), and it's told 
the bt_* calls return -1 on error, but how do I get the actual error is 
nowhere explained. Especially for things like NGM_HCI_NODE_GET_BDADDR, I 
don't know what the output data structure to bt_devreq looks like, and 
how to get any error codes out, the call like I do is not touching the 
output buffer.

Also, what I couldn't get done using the example code in [2] is to make 
this work from userspace, even the example only returns data as root.

I'm on FreeBSD 14.0-STABLE arm64 if it matters.

Could I please get some help on how to work with the BTLE stack properly?

Best regards,
Gergely

[1] https://kvurd.com/blog/tilt-hydrometer-ibeacon-data-format/
[2] https://github.com/takawata/FreeBSD-BLE/tree/master/le_enable
[3] 
https://github.com/gczuczy/aegir/blob/fermd/controllers/fermd/Bluetooth.cc