Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32wl/STM32WL5x_CM0P/RCC/EXTCFGR#0x0
Extended clock recovery register
HCLK3 shared prescaler (AHB3, Flash, and SRAM2)
[dual core device only] HCLK2 prescaler (CPU2)
HCLK3 shared prescaler flag (AHB3, Flash, and SRAM2)
CLK2 prescaler flag (CPU2)
https://github.com/modm-io/cmsis-svd-stm32