My overall goal is to make a custom board, but I've got started using off the shelf boards to put together a prototype system.  The final board will have a STM32F769 as the micro, but I'm working off of a board that has a STM32F767.  The only real difference is the lack of DSI-HOST on the latter.  While being able to work on MIPI-DSI displays is one of the goals, it's not entirely necessary at this stage.  The STM32F767 board that I'm using is one commonly found on Ebay and Aliexpress and others like it.  Here's some examples from Ebay.  The board is cheap (around 25-30USD), has SDRAM on board, QUADSPI capable flash, JTAG connector among other features.  To that board, I added an Adafruit TFT Friend, giving me a 40-pin FPC connector and a LED backlight drive circuit.  Next up is an Adafruit Resistive Touchscreen Controller, adding in, ya know, resistive touch screen control.  Finally whack in a 4.3" touch screen with resistive overlay and you've got all the hardware bits to get going.  I have a whole bunch of 4.3" touch screens surplus from various manufacturers and they are all pretty close to the same so one could call it almost a "standard" display.  The STM32F767 board can be powered over USB and the whole system consumes under 500mA current, so this option is viable.  On my bench, I'm running it from a bench supply.  Last hardware item is my ST-LINK V3SET debugger.  Here's what the mess looks like all put together:

To date, I've been able to get the SDRAM up and going and run some basic tests on the LCD.  There is an issue with the QUADSPI flash that's on this board.  That's detailed in another project of mine found here

More updates to come!