Changing the layout of a Taxonomy Term Page

Question

By default my taxonomy term page lists all articles using this term in 2-columns. I would like to change it to a 1-column layout.

(1) I have created a custom display layout for the taxonomy group:

(2) And selected the one column layout:

Still it doesn't work. Any other changes, like adding a field, do work though. What am I missing?

Note: I did clear the cache.

Answer 1

Thanks to @prkos, it turned out that the root of the problem was located inside the Bootstrap Sub-Theme.

Someone created a (hacky) template override for one specific content type in a generic manner. By renaming the file views-view-unformatted.html.twig to views-view-unformatted--SOME-CONTENT.html.twig it kept the override for the mentioned content item, but also made layouts of other, generic content types work as intended.