2
You could try this instead
if (!is_front_page() && is_home()) {
get_template_part('template-parts/blog-categories');
}
Explanation for the difference between front_page an home is here: https://wordpress.stackexchange.com/a/239838
if you set a page as a blog-page it is "home", in your case the landing-page is the so called "...
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