As per Trouble with Python build matrix being respected by jobs , stages are not considered an axis so you cannot use the matrix to add jobs to more than one stage.
Maybe you can specify stage at top level to change the name of the default stage.
As per Trouble with Python build matrix being respected by jobs , stages are not considered an axis so you cannot use the matrix to add jobs to more than one stage.
Maybe you can specify stage at top level to change the name of the default stage.