Resolved! [Documentation Typo] UART8 TX DMA for STM32F413/423
In the STM32F413/423 reference manual ( RM0430 Rev 8), there are two UART8_RX options, but no UART8_TX option. This seems like a typo, since all other UART instances have both a TX and RX mapping.Also, CubeMX lets you assign UART8_TX to stream 0.