George Stephanis

Simple 404 Keyword Insertion creates a page called “404-page” on activation. When a visitor hits a 404, the plugin serves that page with a <code>[404-keywords]</code> shortcode replaced by the sanitized keywords from the request URI. This helps create SEO-friendly 404 pages that reflect the content the visitor was looking for.

Simple 404 Keyword Insertion

Builds a custom 404 page based on the request URL, inserting the keywords from the failed request into your 404-page content.

Seerox

WP Dynamic Keywords Injector inserts the keyword from browser’s address bar, if not given in URL then the spintax will be placed and if both not found then the default keyword will be placed. Also this plugin will change the title tag and page title if they are given in browser’s address bar.
<iframe loading="lazy" class="youtube-player" width="750" height="422" src="https://www.youtube.com/embed/4DMTdlvIisY?version=3&rel=1&showsearch=0&showinfo=1&iv_load_policy=1&fs=1&hl=en-US&autohide=2&wmode=transparent" allowfullscreen="true" style="border:0;" sandbox="allow-scripts allow-same-origin allow-popups allow-presentation allow-popups-to-escape-sandbox"></iframe>
This will allow users to insert dynamic keywords not only in page title, page content but also in meta title for the landing pages. Used to be promoted on adwards. 
This functionality has been implemented through shortcode given below is a sample shortcode.
[seerox_wpdki_dyn_keywords default="These are default keywords. Test1, Test2" spintax="{Text|to|Spin}"]
To put the default value please change the "default" attribute value of shortcode. 
To add spintax please change value of "spintax" attribute.
To inject keywords from URL, please use "dyn_keyword" query string parameter from browser’s address bar. e.g http://example.tld/sample-page/?dyn_keyword=your_desired_keywords
To inject page title from URL, please use "page_title" query string parameter. sample link is given below. 
http://example.tld/sample-page/?page_title=your_desired_page_title
To change meta title from URL, please use "title" query string parameter. sample link is given below. 
http://example.tld/sample-page/?title=your_desired_meta_title
Please Note: These all query string parameters can be used with combinations as well. The sample link is given below. 
http://example.tld/sample-page/?dyn_keyword=your_desired_keywords&page_title=your_desired_page_title&title=your_desired_meta_title
WPDKI providing you ability to define search keyword "search_keyword" in Page URL as parameter which you can then use in meta title, page/post title and content as "SEARCH_KEYWORD". An example is given below for your better understanding.
WPDKI brings a new feature, Whitelisting Keywords functionality for Title and Page Title. In this feature admin can control to show Replace Keywords in Title and Page Title. If this functionality is turned on Plugin will allow to display only Keywords which are whitelisted by admin. If this functionality is turned off then those keywords will show in Title and Page Title which you put in Page URL as parameter.If this functionality is turned on and no keyword is define in Whitelist Keyword box then Default Title and Page Title will Display.
http://example.tld/sample-page/?search_keyword=Search+Keyword 
This keyword can be use in title, page_title and in default value of dyn_keyword shortcode like. 
http://example.tld/sample-page/?title=Its+SEARCH_KEYWORD+title&page_title=SEARCH_KEYWORD+Heading&search_keyword=Search+Keyword
[seerox_wpdki_dyn_keywords default="This SEARCH_KEYWORD is Draft."]
<a href="https://tastewp.com/new?pre-installed-plugin-slug=wp-dynamic-keywords-injector&redirect=admin.php%3Fpage%3Dseerox_wpdki_settings&ni=true" rel="nofollow ugc">Click here</a> to play with it
<h4>PRO</h4>
WP Dynamic Keywords Injector plugin is also available in a professional version which includes more functionality, and more flexibility!
<ul>
<li>Unlimited Landing Pages</li>
<li>Unlimited Multiple Sub Keywords</li>
<li>Interface to Manage Keywords</li>
<li>Perfect Quality Scores</li>
<li>Dynamic Images</li>
<li>Dynamic Videos</li>
<li>Dynamic Spintax</li>
<li>Keyword Groups</li>
<li>HTML enabled Keyword Fields</li>
<li>IFrame Support</li>
<li>WP Shortcodes Support</li>
<li>Generate Dynamic Links</li>
<li>Download all possible Links</li>
<li>Import and Export Keywords</li>
<li>Relevant Posts Links list ShortCode</li>
<li>Relevant Random Post Link ShortCode</li>
</ul>
<a href="https://wpdki.com/" rel="nofollow ugc">Upgrade to Pro</a>

WP Dynamic Keywords Injector

Most people use RankMath SEO Nowadays for lightweight.

Please make this compatible.

Why still no support for RankMath SEO

WP Dynamic Keywords Injector inserts dynamic keywords, spintax, page title and title tag.

Simple 404 Keyword Insertion vs WP Dynamic Keywords Injector