I would like to program the display on the STM32H753I-EVAL2 to the bare wire, not using TouchGFX. What document would have the required information?

The reference manual of the STM32 chip and the datasheet of the display are going to be the primary documents to consult.

I'm thinking that document would be the RM describing the LTDC and DSIHOST type interfaces, and the data sheets for the assorted LCD panels ST utilizes, along with touch controllers as appropriate.

That's usually sufficient for "bare metal", raster displays are much the same as they were decades ago, the pixel clocks have to scale to handle expanding resolutions.

From a code level there should be pretty basic code to get the frame buffer and timing set up in the BSP (real magic is the clocks, PLL, etc), and example code in the \H743I-EVAL\Applications directories, either explicitly or as part of the JPEG decode, or BitmapFileOnSDCardToDisplay type examples. The BSP code, for these or close sisters, would have line, dot and circle drawing primitives, plotting into the frame buffer directly, also some text/font into the frame buffer.

STM32Cube_FW_H7_V1.8.0\Projects\STM32H743I-EVAL\Applications\Display\LTDC_PicturesFromSDCard

STM32Cube_FW_H7_V1.8.0\Projects\STM32H743I-EVAL\Applications\Display\LTDC_Paint

STM32Cube_FW_H7_V1.8.0\Projects\STM32H743I-EVAL\Applications\LibJPEG\LibJPEG_Decoding\Src\main.c

STM32Cube_FW_H7_V1.8.0\Drivers\BSP\STM32H743I-EVAL\stm32h743i_eval_lcd.c

STM32Cube_FW_H7_V1.8.0\Drivers\BSP\Components\ampire640480\ampire640480.h

STM32Cube_FW_H7_V1.8.0\Drivers\BSP\Components\ampire480272\ampire480272.h

 How To use this driver:

 -----------------------

  - This driver is used to drive directly an LCD TFT using the LTDC controller.

  - This driver selects dynamically the mounted LCD, AMPIRE 640x480 LCD mounted

   on MB1063 or AMPIRE 480x272 LCD mounted on MB1046 daughter board,

   and uses the adequate timing and setting for the specified LCD using

   device ID of the STMPE811 mounted on MB1046 daughter board.

Thanks. I loaded the LTDC_Paint example. It didn't seem to work out of the box. I'm looking into that.

I've noticed that there are examples for stm32h743, but not for stm32h753. Is it a safe assumption that stm32h743 code will work directly on the stm32h653?

I scanned the titles of the stm32 documents and found this: https://www.st.com/resource/en/application_note/an4861-lcdtft-display-controller-ltdc-on-stm32-mcus-stmicroelectronics.pdf It covers stm32f7 boards. I'm assuming that the stm32h7 EVAL works the same way. Anybody know?