[Docs] User Guide Section 7.1 has outdated nRF Util installation instructions (pip-based, deprecated)

[rquidute]

Description

Section 7.1 ("Instructions to Flash the Firmware NRF52840 RCPDongle") of the Matter TH User Guide still documents the deprecated PyPI-distributed nrfutil, which no longer matches Nordic's current tooling:

python3 -m pip install -U nrfutil
nrfutil install nrf5sdk-tools

Nordic has since replaced the pip-installable nrfutil package with nRF Util, a standalone self-updating executable distributed directly from Nordic (not via pip). The old nrf5sdk-tools/nrfutil dfu usb-serial command surface referenced later in the same section is tied to the deprecated package and doesn't carry over to the current tool.

This was raised as item 4 in #1075.

Current guide text (Section 7.1)

docs/Matter_TH_User_Guide/Matter_TH_User_Guide.adoc:941-962

. nRF Util is a unified command line utility for Nordic products. For more details, refer to the following link— https://www.nordicsemi.com/Products/Development-tools/nrf-util
. Install the nRF Util dependencies on the user's system using the following commands:

python3 -m pip install -U nrfutil
nrfutil install nrf5sdk-tools
...
nrfutil dfu usb-serial -pkg <FILE NAME> -p /dev/ttyACM0

Requested change

• Update the install instructions to reference the current standalone nRF Util executable (curl/direct-download install per Nordic's current distribution method), replacing the pip install nrfutil step.
• Update the dongle-flashing command to the current nRF Util syntax (successor to nrfutil dfu usb-serial), verified against real hardware since Nordic has changed command-set naming across nRF Util releases.
• Clarify that RCP dongle flashing can be performed from a separate Mac/PC (not necessarily the Raspberry Pi running the TH) before connecting the dongle to the Pi.

History / context

These instructions have been present essentially unchanged since the very first commit of the repo (Sep 2023). Most recently touched in PR #425 (Oct 2024), which updated nRF Connect Desktop links and reformatted this section but kept the same pip-based nrfutil install approach.

Related

Split out from #1075 (item 4).