Sadly it’s hard or even impossible to stop the OEM hardware to ‘speak’.
Original carkit sends it’s messages and also the KI controller does that. This causes the ‘flickering’ (in the FIS content and also the REV cam).
I could think of one way to literally ‘bypass’ this issue, I’m not familiar with this solution.
At the skpang site they offer a ‘duo-can’ board. This should make it possible to create a ‘bridged’ setup.
This would make it possible to block / filter unwanted messages (like the messages coming from your carkit while Raspberry is speaking):
But than again, it’s just a theory…