Hello, I recommend review the SDK example for the LPC54628, there is an example about the interrupt.
I reviewed the documentation and on chapter 25.7.9 Break generation and detection mention the next.
Both the beginning and end of a received break are noted by the DELTARXBRK status flag, which can be used as an interrupt.
And on chapter 25.7.10 LIN bus metioned the next.
When a break is requested by setting the TXBRKEN bit in the CTL register, then sending a dummy character, a 13 bit time break is sent.

Best regards,
Pavel