STM32 HAL Using ADC with DMA affects UART transmission
Based on the followings:


the UART is working if you are using it without interrupts along with the DMA, and
if DMA is not used the UART works with interrupts.


The DMA interrupts possibly happens so often that it do not let the UART IRQ to be executed as the CPU is always busy to handle DMA interrupts.

Giving higher priority to UART IRQ should solve the issue.