CMS v4 RSS feed with custom tag "category"

Hello!

I want to use the tag “category” of a RSS feed in my layout but I can’t find the explanation how.
The tag is in the item list and looks like:

<category domain="desk">SI</category>

I v3 we used html and javascript to handle that with [category|]
How to use that in the v4 RSS ticker widget?

Thank you.

It seems that I need to create my own module that supports the additional tag.
The “allowed attributes” field is not used in 4.0.12
RssProvider.php
Is that right?
If right, I think that I need to copy

modules/rss-ticker.xml
modules/templates/article-elements.xml
lib/Widget/RssProvider.php
lib/Widget/DataType/Article.php

to custom folder and extend it with the additional tag that I need.
In RssProvider.php I am able to modify the tag content and add the new variable to Article.php

Can that be the right way or am I completely wrong?

I have that from developer documentation Creating a module