Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/STMicroelectronics/STM32F303/TIM8/OR#0x0
option registers
TIM8_ETR_ADC2 remapping capability
TIM8_ETR_ADC3 remapping capability
https://github.com/cmsis-svd/cmsis-svd-data