How to add content of nested terms to Taxonomy term View
Finally found the answer and it is almost the same than for D7:


Edit the existing view Taxonomy Term (admin/structure/views/view/taxonomy_term/edit)
In Advanced, add the field Content: Has taxonomy term ID (with depth) using all the settings from already added Content: Has taxonomy term ID using the same settings. You can limit the depth by setting the depth parameter.
Remove old field Content: Has taxonomy term ID using the same settings
Set Use aggregation to yes to avoid duplicates