The devices are very similar to the iTag series. Gadgetbridge does not support these devices at the moment.
There are various models available called "Nut Nutale", "Nut Find3", "Nut Mini" and "Nut Smart", there's also probably a "Nut Find2". The devices might also be sold under the names of "Nut Find 3", "Nutale Focus" and "NutMini".
As with the iTag series, the Nut devices function as low-powered BLE beacons with the option to make sound and/or flash lights to locate the thing they're attached to.
Purchasing of these devices is not recommended. They do not use standard methods for providing the needed functionality and Gadgetbridge does not support setting the devices up, the devices require sign-up to use the proprietary app.
There's also the issue of account-based DRM, the devices get locked to a single account and have no official way of reuse. The price is also extraorbitant when iTag devices are 5-10x cheaper.
The OTA firmware images
firmware_sys.zip use the AES key
16e92d2456e3d7a5, "standard" Nordic DFU is used for firmware upload.
Nut Mini 3
Based on the nRF51802 MCU. Requires an authentication key to work. You can get the authentication key by just capturing a hci_dump, when you just connect to the device it will contain only three packets. The first two are the challenge (starts with
0x01) and the response (begins with
0x02), third contains
0x03 0x55 that just says the authentication was correct (
0x03 0xaa means failure).