Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32u5/STM32U535/RTC/SECCFGR#0x0
RTC secure mode control register
ALRASEC
ALRBSEC
WUTSEC
TSSEC
CALSEC
INITSEC
SEC
https://github.com/modm-io/cmsis-svd-stm32