In file:
https://github.com/UAVCAN/platform_specific_components/blob/legacy-v0/stm32/libcanard/canard_stm32.c#L281

I think it should be:
FILTER_CONFIG_BXCAN->FA1R = FILTER_CONFIG_BXCAN->FA1R | (1 << 0);

because in some stm32 it have 2 can, but control can2 filter active bits in CAN1 FA1R register .
So take care of slave can.