Hello @achovy and welcome to the Community :),
-->There's an error like this (handle_GPDMA1_Channel12' undeclared (first use in this function); did you mean 'handle_GPDMA1_Channel0'?)
Thank you for bringing this issue to our attention with GPDMA: Standard Request Mode. I reported this internally.
Could you please add in main.c under Private variables this line:
DMA_HandleTypeDef handle_GPDMA1_Channel12;

and in STM32u5xx_it.c under external variables this line:
extern DMA_HandleTypeDef handle_GPDMA1_Channel12;

Also you can use the GPDMA Linked-List mode without issue. For that I recommend you to refer to the DCMI_ContinousCap_EmbeddedSynchMode example. This example can help you to start with GPDMA and DCMI.
Also, please take a look at AN5593 How to use the GPDMA for STM32 MCUs precisely section GPDMA configuration for graphic peripherals.

Internal ticket number: 180281 (This is an internal tracking number and is not accessible or usable by customers).
Thank you.
Thank you.
Kaouthar