It would be a good match for some kind of input capture peripheral (the MCU does not have input capture per-se but it is an Cortex M7 so you can certainly build

It would be a good match for some kind of input capture peripheral (the MCU does not have input capture per-se but it is an Cortex M7 so you can certainly build that out of interrupt matrix and some clever configuration of DMA engine) or for abusing SPI USRT if it can support such extremely long frames (which it probably can).