Is there a simple way to retrieve the term ID?

Nevermind, I was not thinking straight…

If I fetch the meta value it works like a charm. This way I can use a block to populate a Blocksy theme shortcode, never showing the shortcode in the editor.

<?php
$category = get_lzb_meta( 'select_category' );
$number = $attributes[ 'post_count' ];

echo do_shortcode( '[blocksy_posts term_ids="' . $category . '" limit="' . $number . '"]' );