How do I programmatically update the rendering language?
Yes, this is not a handler setting. This is configured directly in a display.
To update a View programmatically use the storage property of the View object (which is by the way a reference to the config object discussed in the comments) and get a reference of a display (the master display is default):
$view = \Drupal\views\Views::getView('myview');
$storage = $view-&gt;storage;
$display = &amp;$storage-&gt;getDisplay('page_2');
$display['display_options']['rendering_language'] = '***LANGUAGE_language_content***';
$storage-&gt;save();