Luke Rumley

This plugin allows you to assign a theme to a specific category. It is actually @MikeLopez’s code, I just tweaked it to work on WordPress 3+.
This version adds child theme capability, and the ability to assign a theme to a new category as it is created. It also ignores pages and the home page, so the current theme is applied there.

GYS Themed Categories

This plugin allows you to assign a theme to a specific category.

Elementor

Hello+ is a free WordPress plugin designed to work seamlessly with Elementor’s <a href="https://profiles.wordpress.org/elemntor/#content-themes" rel="nofollow ugc">Hello suite of themes</a>. It provides a solid foundation for crafting unique, purpose-driven websites using Elementor’s drag-and-drop site builder.
Hello+ includes specialized Hello widgets such as a Header, Footer, Zigzag, Form Lite, and more. Hello widgets help you build faster and create polished, professional websites.
To use Hello+, you’ll need to <a href="https://profiles.wordpress.org/elemntor/#content-themes" rel="nofollow ugc">install one of Elementor’s Hello suite of themes</a>.
<h3>Copyright</h3>
This Plugin, like WordPress, is distributed under the terms of GPL. 
Use it as your springboard to building a site with Elementor.

Hello Plus

Hello+ is a free WordPress plugin designed to work seamlessly with Elementor’s Hello suite of themes.

GYS Themed Categories vs Hello Plus