To start reverse-engineering the circuit behind this board, I started by taking photos of the bottom and top layers, and inking over with my Surface:
MIPI-HDMI Bridge Chip
You can see that the connector on the right does indeed support two MIPI channels, each consisting of 4 data pairs & 1 clock pair. The MIPI bridge chip is connected to the MCU via I2C, and there is minimal support circuitry (only a crystal, a few buck regulators, and some passives for the PLL).
On the upper-left you can see that things get a bit more complicated. A lot of this is to support many different kinds of displays, and provides various voltages for backlighting, OLED biasing, etc. It also supples two sets of bi-directional GPIOs, one at 1.8V, and one at 3.3V.
Finally we have the "STM32" MCU which is the brains of the board:
Those four pads on the right look interesting... could they be SWD perhaps?
(VDD, GND, PA13/SWDIO, PA14/SWCLK)