Removed the Taxable model, you should create a custom Taxonomy model in your project that extends Lecturize\Taxonomies\Models\Taxonomy and contain your project-specific morphedByMany relations, e.g. posts. Don't forget to override the config value of config('lecturize.taxonomies.taxonomies.model') accordingly.
On the taxable pivot table a primary key has been added, make sure you have no duplicates in that table before publishing and running the new migrations! Also, timestamps have been added to the pivot table.
If you are using the get_categories_collection() or build_categories_collection_from_tree() helper function or Taxonomy::getTree() review the slightly adapted signatures. Instead of a taxables class (e.g. \Post:class) through the $taxable argument, we now ask for a $taxable_relation (e.g. the posts relation on your custom taxonomy model). If you continue to pass a class name like \Post:class we'll try and guess the relation by using Str::plural().