Sorry,
I do have the same problems.
Before Cubase 12 I used Cubase 11 with y mini Mac 2018 - Catalina.
Now I'm using a Mini Mac 2020 M1 Silikon (no intel). The DAW settings for Cubase on my MK49II Midi Keyboard do not run. I was forced to use on of the user modes (for Example User mode1 ) so, that the new midi remote controll of cubase was able to be programmed. The Faders now run, so as the track and Global controll.
But my TRANSPORT Buttons can not be activated and programmed with the midi remote controll of cubase. Even the can not be chandged with the Arturia Midi controll center. The only support informations I got are: using Mackie controll in cubase an changing F1,F2,F3,F4 category and commands as shown in an old documentation. If I do this, nothing works at all. Then the VST Instruments are chrashing. I was searching for an answer - reinstalling the old Mac and now the new one. Nothing changed. I also tried rosetta mode. No results. I am also disappointed that the Drum pads are not working anymore also the the accord mode for pads do not have and function in cubase 12. I am still waiting for an improvement.