How to test the flow control of NRF54L15-PDK-0.8.1-ZEPHRY2.8.0 UART00?

I added my own overlay to the website routine "ncs-fund\v2.8.x-v2.7.0\l5\l5_e1_sol". The contents are as follows

///////////////////////////////////////////////////////////////
&button0 {
        status = "disabled";
};

&button1 {
        status = "disabled";
};

&button2 {
        status = "disabled";
};

&button3 {
        status = "disabled";
};

&spi00 {
        status = "disabled";
};

&pwm20 {
        status = "disabled";    
};

&uart00 {
    compatible = "nordic,nrf-uarte";
    status = "okay";
    current-speed = <115200>;
    pinctrl-0 = <&uart00_default>;
    pinctrl-1 = <&uart00_sleep>;
    pinctrl-names = "default", "sleep";
    hw-flow-control;
};

&pinctrl {
    uart00_default: uart00_default {
            group1 {
                    psels = <NRF_PSEL(UART_TX, 2, 8)>,
                            <NRF_PSEL(UART_RX, 2, 7)>,
                            <NRF_PSEL(UART_RTS, 2, 10)>,
                            <NRF_PSEL(UART_CTS, 2, 9)>;
            };
    };

    uart00_sleep: uart00_sleep {
            group1 {
                    psels = <NRF_PSEL(UART_TX, 2, 8)>,
                    <NRF_PSEL(UART_RX, 2, 7)>,
                    <NRF_PSEL(UART_RTS, 2, 10)>,
                    <NRF_PSEL(UART_CTS, 2, 9)>;
                    low-power-enable;
            };
    };
};
///////////////////////////////////////////////////////////////
I changed to use uart00 in main.c
Finally, I used the USB to TTL serial port board to connect the pin of the PDK board, open or not open the flow control, I could not see the print
I tried both sets of pins on the spec,I'm disabled. uart20 will fail to compile
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