Ok, with some try on localhost I was able to spot part of the problem. In this code
{% include 'partials/taxonomylist.html.twig' with {base_url: my_url, taxonomy: 'tag', children_only: true} %}
I need to specify more than one category in base_url.
If for instance I write this value in my_url http://localhost:8888/gravsite/news/blog the posts in category "blog" are correctly displayed according their tags, but nothing is working for the other category "features"
I need to alter the code above to add more than a category in route my_url
The problem is that the taxonomy list plugin works with one category only and it is not possible to add new categories to the default route. I tried to add a boolean | but the field rout to blog doesn't accept it