John Havlik

Reviewing the behavior in WPML on my testbed, it appears things work correctly (though I only tested the Post post type, others should work as well). Switching to a different language doesn’t cause the term hierarchy to get jumped. I’m going to need a little more information on your setup to try to recreate it on my testbed. It would be helpful to know if when you only include the deepest term, is just the breadcrumb for the product archive page missing, or are some category breadcrumbs missing as well?

Breadcrumb NavXT would not add the custom taxonomy itself. You can either use a plugin that provides a GUI for creating custom taxonomies, or checkout the WordPress Documentation on how to use the register_taxonomy function to add a custom taxonomy to your post type.

As discussed in another thread: https://wordpress.org/support/topic/breadcrumblist-errors-on-the-last-item-because-it-is-missing-the-item-tag/#post-10638393 the unlinked breadcrumbs should not contain structured data (otherwise Google’s tool will throw errors which is expected per the schema.org spec). The latest version of Breadcrumb NavXT should be using a more basic <span class="%type%">%htitle%</span> by default rather than something with schema.org markup.

For the home page, Breadcrumb NavXT already uses get_home_url() to get the home URL. If the multilingual plugin is not translating the URL provided by that WordPress function, that’s on the multilingual plugin. Polylang apparently doesn’t handle translating get_home_url()‘s output (the Polylang specific extension plugin for Breadcrumb NavXT has to deal with the home URL). WPML does translate get_home_url()‘s output.

In general, root pages that are set within the Breadcrumb NavXT settings page are not going to get automatically translated without an extension plugin (the multilingual plugins have no way of knowing what to do here as WordPress doesn’t have a concept of root pages for CPTs).

This is the expected behavior of Breadcrumb NavXT. Primary terms in a taxonomy are not a construct that is present within WordPress code, so this isn’t something the core of Breadcrumb NavXT will pick up on without additional code. An older method of dealing with this was to change the order that the terms are returned to take advantage of how Breadcrumb NavXT selects a term. More recently, the bcn_pick_post_term filter was introduced and can be used to tell Breadcrumb NavXT what term to use within a taxonomy.

Order Bender (see https://github.com/mtekk/Order-Bender/blob/master/order-bender.php) provides an interface for setting the primary term, re-orders the term output (to place the primary first), and uses the bcn_pick_post_term filter. You should be able to modify Order Bender to integrate with whatever solution you’re using to set a primary term (likely just need to change what post meta is used in the function hooking into bcn_pick_post_term).

My philosophy is to not include 3rd party specific plugin code in the core Breadcrumb NavXT plugin. In general, most things are automatically translatable. Beyond what is possible using the WordPress API/concepts in core is the ground for extension plugins. There are premium extension plugins to Breadcrumb NavXT that fill in support for a few concepts that Polylang and WPML don’t automatically pick up on (translating root pages, translating breadcrumb templates).

is_front_page is a function, you need the parentheses after it, e.g. your first line should be:

<?php if(function_exists('bcn_display') && !is_front_page()):?>

@alriksson In the article I linked to, the last code example moves the if statement outside of the div block:

<?php if(function_exists('bcn_display') && !is_page(PAGE_ID1) && !is_page(PAGE_ID2)):?>
<div class="breadcrumbs" typeof="BreadcrumbList" vocab="https://schema.org/">
    <?php bcn_display();?>
</div>
<?php endif; ?>

This will prevent the div (or if you wish to, replace div with nav) element from being output when the breadcrumb trail is not included on the page due to whatever condition you place in the if statement.