Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32wl3/STM32WL33/MR_SUBG/RSSI_FLT#0x0
RSSI_FLT register
Peak decay control for OOK: 3 slow decay; 0 fast decay
Gain of the RSSI filter
https://github.com/modm-io/cmsis-svd-stm32