Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32h5/STM32H503/LPUART/LPUART_BRR#0x0
LPUART baud rate register
LPUART baud rate division (LPUARTDIV)
https://github.com/modm-io/cmsis-svd-stm32