First we need to establish good terminology.

There are oldest transmission with external TCU, those are mostly controlled by on/off solenoids. We have some untested unfinished code to handle those, this work is totally halted as of Dec 2022. There is hope to revive it in 2024 :)

Then we have some complex transmissions with external TCU like Honda, or clutch-to-clutch like Aisin 09G/09M, and modern transmissions with TCU located inside the transmission assembly. For those we are focusing on CAN integration only, not looking to re-invent the TCU itself.