Slick RSS New (fork from Slick RSS by users 4.0.1)

Slick RSS New is a fork of the "Slick RSS by users" extension, version 4.0.1 (thanks to its brilliant author).
It's presented as a web page displaying a list of feeds on the left side and articles in tile-like columns on the right. Many options are available:
- Standard and dark modes,
- Number of columns (up to 5),
- Maximum article height,
- Display or hide images, objects, and iframes in articles,
- Filter articles by category,
- Read later list management,
- Groups management with ability to show only unread articles
- Management of a group "all articles"
- Open links in background,
- Mark articles as read or unread upon clicking,
- Mark all articles in feed as read on the first click or after seconds,
- Automatic selection of the first feed containing unread articles,
- ...