Issues in Uart configuration at a ATmega4809 microcontroller

Question

hope you are having a great time getting to the point these past days I have been working with a MicroChip Curiosity Nano (ATmega4809) trying to enable a communication by UART ports on Microchip Studio, when the only way I could establish this is when I use al the default configuration (8 bits frame,none parity,1 stop bit) but when try to configure to a 9 bit frame I started to recieve some weird characters.

I have done several changes on this configuration according to datasheet based on registers managment but always the same results.

void USART0_init(void)
{
    USART0.BAUD = (uint16_t)USART0_BAUD_RATE(9600);
    USART0.CTRLB |=  USART_RXEN_bm | USART_TXEN_bm;
    
    //Tries I have done
    //#define USART_CHSIZE_gm 0x07
    //USART0.CTRLC |= USART_CHSIZE_gm;
    //USART0.CTRLC |= (7<<USART_CHSIZE_gm);
    //USART0.CTRLC |= (1<<USART_CHSIZE2_bm) | (1<<USART_CHSIZE1_bm) | (1<<USART_CHSIZE0_bm);    
    
    PORTA.DIR |= PIN0_bm;
    PORTA.DIR &= ~PIN1_bm;
    
}

This code is the UART port's inizialization, and the lines I have commented are about the configuration I need to get 9 bits frame communication, also I mentioned before when I commented this part it works correctly to 8 bits frame communication.

Thanks for taking the time and have a nice day.