It's an interesting challenge, but MIPI DSI is sort of the right interface for small size displays too high resolution to drive with SPI. There are a range of

It's an interesting challenge, but MIPI DSI is sort of the right interface for small size displays too high resolution to drive with SPI. There are a range of Cortex-M4 and M7 MCUs that have DSI output (e.g. https://wiki.st.com/stm32mpu/wiki/DSI_internal_peripheral https://wiki.st.com/stm32mpu/wiki/DSI_internal_peripheral). The solution is probably just better documentation for the panels and their DDICs.