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.

Darken-x

After I updated WordPress to 5.3, I thought something had gone wrong with the update when I saw those borders in the admin area, the blue color of texts on the form elements and the lack of design subtlety of the UI. So I decided to create a plugin that would undo that.
The plugin styles the WordPress 5.3+ admin panel back to how it was before the 5.3 update. So, if you also disliked the vivid blue texts and strong borders of the form elements, like buttons, inputs and selects, or found them to be way too prominent, this back-to-the-good-old-days “legacy” plugin will allow you to update WordPress to 5.3 and benefit from its code updates, while still retaining all of the previous version’s backend UI styles.
Very very lightweight and easy to use.

Old Style Admin UI

Just activate the plugin and voila! you have the pre-5.3 admin buttons and tables and everything else.

Works perfectly

I absolutely can't stand the new 5.3 design... thank you SO much for giving me back the normal styling! :)

Thank you!

If you didn't like the new Wordpress 5.3 accessibility blue style for the buttons and other parts of the admin UI, this plugin is for you.

Radio Buttons for Taxonomies vs Old Style Admin UI