Change default query parameters

You can filter request and unset m there, which will remove it from the query. This is a simple example that will remove it in all cases, you probably want to narrow the check down with something else, like checking if pagename is also set:

function wpd_request_filter( $request ){
    if( isset( $request['m'] ) ){
        unset( $request['m'] );
    }
    return $request;
}
add_filter( 'request', 'wpd_request_filter' );

You can var_dump( $request ) in the filter to see what it contains for different types of requests.