No idea what Tesla does, the rest of the car indutry cares about stuff Tesla apperently does not, given the public reports on lack of software quality.

NVidia uses a mix of QNX (for production) and GNU/Linux (for development) for their vehicles software.

https://developer.nvidia.com/drive/driveos

Note the safety critical remark for QNX, when human lifes are at stake, one gets to use OSes where safety matters as first priority.