Unrecognized item “timeout” in “qSupported” response on my Arduino Uno

aswell Testing code on my arduino uno for my first using with simple hello world serial print, but while attempt to debugging but the debug console sending this:

PlatformIO Unified Debugger -> https://bit.ly/pio-debug
PlatformIO: debug_tool = avr-stub
PlatformIO: Initializing remote target...
Ignoring packet error, continuing...
warning: unrecognized item "timeout" in "qSupported" response

as if you don’t about my code for input:

#include <Arduino.h>
#include "avr8-stub.h"

void setup() {
    debug_init();
    Serial.begin(9600);
}

void loop()  {
    Serial.println("Hello World!");
    delay(1000);
}

or maybe the incorrected configuration file:

; PlatformIO Project Configuration File
;
;   Build options: build flags, source filter
;   Upload options: custom upload port, speed and extra flags
;   Library options: dependencies, extra library storages
;   Advanced options: extra scripting
;
; Please visit documentation for the other options and examples
; https://docs.platformio.org/page/projectconf.html

[env:uno]
platform = atmelavr
board = uno
framework = arduino
debug_tool = avr-stub
debug_port = COM5

lib_deps =
    jdolinay/avr-debugger @ ~1.4

overall, we need to respond this question asap.
many thanks,
me

You cannot use both the Serial and avr-stub for debugging because avr-stub exactly uses the serial connection to speak to the debugger client (gdb).

This is documented behavior.

This has also been thoroughly discussed in multiple topics in this forum already.