A very simple variant would be described here: https://hoolite.be/wordpress/add-custom-meta-tags-to-via-functions-php/
However, this would mean that all pages of your website would have the same information. This could be suboptimal. If you want to have separate information for each page, you would have to add meta information to pages and posts. Then you would have the input option in the backend and this input would then be output in the frontend. An introduction to this can be found here: https://wp-dev-recipes.serversideup.net/plugins/wordpress-custom-post-meta-fields/
The best way to solve this is as an individual plugin. An introduction can be found here: https://developer.wordpress.org/plugins/
Title tags and description meta tags are theme dependent. If your theme adds theme support for ‘title-tag’, you can use the “wp_title” or “wp_title_parts” filters to alter the title tag value.
WP by default does not output a meta description, but your theme might do so on its own. If it does, how to alter it depends on your theme. If not, you can output the tag yourself from the “wp_head” action hook. Use a small priority arg value so it’s output relatively early among all the other wp_head output.
It possible to alter theme behavior with a child theme, or in most cases a plugin. If custom templates are involved, a child theme is usually preferable. But templates from a plugin are possible, if a bit cumbersome.
Thanks guys. I used ChatGPT to write a plugin that displays custom SEO title and meta description. Hardly took 5 minutes.
