Step 4: Build and flash

Flash the host firmware. Choose one of the following options:
- Build from source: Run the following commands inside the toolchain shell (step 2.4 in Set up the repository and toolchain), from smha-workspace/project:
```
cd applications/91m1_at
west build -b nrf54lm20dk/nrf54lm20b/cpuapp/ns -p
west flash
```
  If flashing fails because the device has never been programmed with this application or is read-back protected, run west flash --recover once. This application stores no cloud credentials on the host, so there is nothing to lose.
- Pre-built firmware: Download the 91m1_at-nrf54lm20b-* zip from the latest release, extract it, and flash merged.hex. See Release artifacts for what the zip contains.
```
nrfutil device recover --serial-number <host_dk_serial_number>
nrfutil device program --firmware merged.hex --serial-number <host_dk_serial_number>
nrfutil device reset --serial-number <host_dk_serial_number>
```
Open a serial terminal at 115200 baud on VCOM0 of the nRF54LM20B DK and reset the DK.

Checkpoint: The console logs the following once LTE is registered:

<inf> network: Network connected
<inf> cloud: Device UUID: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
<inf> cloud: Provisioning started