Hi @MarkPotts,
LPUART refers to the Low Power UART module, and its functions can be dependent on the board.
I would suggest downloading the SDK Package from MCUXpresso SDK Builder, search for the KL02Z board, select all the middleware that is needed and download the SDK Package.
In the download menu, you can select the "Download SDK Documentation".

Inside "docs", you will find "MCUXpresso SDK API Reference Manual_MKL02Z4.pdf", which is the specific board manual, and latest revision. We recommend always checking the SDK documentation, as the online API manual may be general or not include all the functions in a certain board.
I hope you find this helpful!
Best regards, Julian.