HelgaTheViking

Replace the default taxonomy boxes with a custom metabox that uses radio buttons… effectively limiting each post to a single term in that taxonomy.
A plugin options page allows the user can select which taxonomies she’d like to switch to using the custom radio-button style metabox.
Originally based on the the <a href="https://github.com/stephenh1988/Radio-Buttons-for-Taxonomies" rel="nofollow ugc">class by Stephen Harris</a>
<h4>Support</h4>
Support is handled in the <a href="https://wordpress.org/support/plugin/radio-buttons-for-taxonomies" rel="ugc">WordPress forums</a>. Please note that support is limited and does not cover any custom implementation of the plugin. Before posting a question, read the <a href="https://wordpress.org/plugins/radio-buttons-for-taxonomies/#faq" rel="ugc">FAQ</a> and confirm that the problem still exists with a default theme and with all other plugins disabled.
Please report any bugs, errors, warnings, code problems to <a href="https://github.com/helgatheviking/Radio-Buttons-for-Taxonomies/issues" rel="nofollow ugc">Github</a>

Radio Buttons for Taxonomies

Thank you so much for this plugin, so easy to use and makes creating a single category situations much easier.

Oh this is a life saver!

JUST WORKS

Many thanks to the author for this great plugin. Does one things and does it very well. Works with classic editor and block editor.

5 stars is not enough. Works with Gutenberg

We've been using this plugin for longer than we can remember, never had any issues whatsoever, highly recommended!

Excellent

Replace the default taxonomy boxes with a custom metabox that uses radio buttons... effectively limiting each post to a single term in that taxonomy.

zxial

This plugin provides JSON data to mobile APPs. Here’s the scenarios that you 
could use this plugin: you want to develop a mobile app or app on mac, and the 
app is to show the list of your blogs(in category, tag, or keywords), after 
the app user click one item in the blog list, you would like to show him the 
detail page of the item, but the logos/banners/sidebar of blog is suitable 
only for a desktop other than a mobile device or you want to do something 
different. In the case here, wp_app_json mayble could help.
Code: 
Author: Zxial 
Web: http://zxial.me

WP APP JSON

The WP-APP-JSON is a plugin that provide json data to mobile apps, you can use keywords to search your posts and get detail webpage.

Radio Buttons for Taxonomies vs WP APP JSON