Error when trying to use arduino framework with staging version

I followed the instructions to use the arduino framework with staging version in Espressif 8266 — PlatformIO v6.1 documentation, but I get the following error:

PlatformManager: Installing espressif8266_stage
Error: Detected unknown package ‘espressif8266_stage’

I already installed the staging environment using pio CLI as described in this comment ESP8266 Arduino KRACK fix, compile using PlatformIO? - #4 by glynhudson.

The output of pio platform list shows that there are 3 versions of espressif8266 installed, but I don’t get how to choose between them:

C:\Users\felipe.resende>pio platform list
espressif8266 ~ Espressif 8266
==============================
Espressif Systems is a privately held fabless semiconductor company. They provid
e wireless communications and Wi-Fi chips which are widely used in mobile device
s and the Internet of Things applications.

Home: http://platformio.org/platforms/espressif8266
Frameworks: arduino, esp8266-rtos-sdk, simba
Packages: framework-esp8266-rtos-sdk, toolchain-xtensa, framework-simba, tool-es
ptool, tool-mkspiffs, tool-espotapy, framework-arduinoespressif8266, sdk-esp8266

Version: 1.4.0

espressif8266 ~ Espressif 8266 (Stage)
======================================
Espressif Systems is a privately held fabless semiconductor company. They provid
e wireless communications and Wi-Fi chips which are widely used in mobile device
s and the Internet of Things applications.

Home: http://platformio.org/platforms/espressif8266
Frameworks: arduino, esp8266-nonos-sdk, esp8266-rtos-sdk, simba
Packages: framework-esp8266-rtos-sdk, toolchain-xtensa, framework-simba, tool-es
ptool, tool-mkspiffs, tool-espotapy, framework-arduinoespressif8266, sdk-esp8266
, framework-esp8266-nonos-sdk
Version: 42f080c

espressif8266 ~ Espressif 8266
==============================
Espressif Systems is a privately held fabless semiconductor company. They provid
e wireless communications and Wi-Fi chips which are widely used in mobile device
s and the Internet of Things applications.

Home: http://platformio.org/platforms/espressif8266
Frameworks: arduino, esp8266-nonos-sdk, esp8266-rtos-sdk, simba
Packages: framework-esp8266-rtos-sdk, toolchain-xtensa, framework-simba, tool-es
ptool, tool-mkspiffs, tool-espotapy, framework-arduinoespressif8266, sdk-esp8266
, framework-esp8266-nonos-sdk
Version: 87faed4

Is there something that I’m missing?

Please use the latest documentation in PIO Core 3.5RC Espressif 8266 — PlatformIO latest documentation

If you use PlatformIO IDE, the latest PIO Core 3.5RC will be installed automatically.