Kodo

Slug-Free Permalinks lets you switch selected post types and taxonomies to simple ID based permalink formats.
You can choose between:
<ul>
<li><code>/post/123/</code></li>
<li><code>/post-123/</code></li>
</ul>
The plugin only affects the post types and taxonomies you enable in the settings screen.
Features:
<ul>
<li>Select individual public post types</li>
<li>Select individual public taxonomies</li>
<li>Choose slash or hyphen based ID permalink format</li>
<li>Optionally redirect legacy slug URLs to the current ID based permalink when WordPress can resolve the request</li>
<li>Preserve prefixed permalink bases such as <code>/en/</code> when another plugin adds them</li>
<li>Flush rewrite rules automatically when settings change</li>
</ul>
This plugin is focused on permalink structure only. It does not add content features or front-end UI.
Plugin page (English): https://happas.jp/en/slug-free-permalinks/ 
Plugin page (Japanese): https://happas.jp/slug-free-permalinks/
Development repository: https://github.com/1008k/slug-free-permalinks
This plugin is best suited to new sites, sites still defining their permalink policy, or structured-content use cases where slug management is unnecessary.
If your site already has a large number of published posts and established slug based URLs, review the impact carefully before enabling it. Check existing inbound links, search traffic, social shares, and editorial workflow assumptions.
Known limitations:
<ul>
<li>If a post type slug and taxonomy slug are identical, their ID based rewrite patterns can conflict.</li>
</ul>

Slug-Free Permalinks – Simple ID-Based URLs

Use ID based permalinks for selected post types and taxonomies without managing slugs.

skapator

Convert Greek characters to Latin (greeklish) 
Using <a href="https://github.com/dyrer/greeklish-permalinks" rel="nofollow ugc">greeklish-permalinks</a> with some extra functionality.
<h3>Features</h3>
<ul>
<li>Converts post, pages, taxonomy and category slugs to greeklish automatically</li>
<li>Hooks in the sanitize_title() function</li>
<li>You can use <code>skp_greeklish_slugs($your_text)</code> in your template files (good for dynamic css classes etc.)</li>
<li>Select to strip out 1 letter words</li>
<li>Select to strip out 2 letter words</li>
<li>Define stop words that will be striped out of the slugs</li>
<li>You can modify the translitaration array of regex via <code>apply_filter('skp_greeklish_slugs_expressions', 'your_callback')</code></li>
</ul>
<h3>Filter the regex array</h3>
You can use <code>apply_filter('skp_greeklish_slugs_expressions', 'your_callback')</code> and modify the regex array used to transliterate
<pre><code><?php
function your_callback( $expressions ) {
 // the $expressions parameter is the array with all expressions used

 // view the expressions
 var_damp( expressions )

 // Change/remove items
 $new_expressions = array(
 ...
 '/[μΜ][πΠ]/u' => 'mp',
 '/[νΝ][τΤ]/u' => 'nt',
 '/[τΤ][σΣ]/u' => 'ts'
 ...
 );

 // Add them
 $expressions = array_merge( $new_expressions, $expressions );

 return $expressions;
}
add_filter( 'skp_greeklish_slugs_expressions', 'your_callback' );
?>
</code></pre>
Fork on <a href="https://github.com/skapator/Skp-Greeklish-Slugs" title="Link to github" rel="nofollow ugc">github</a>.
<a href="https://noveldigital.pro" title="Link to github" rel="nofollow ugc">noveldigital.pro</a>

Greeklish Slugs

Translitaration of greek characters to latin for post permalinks with some extra options. (greeklish)

Slug-Free Permalinks – Simple ID-Based URLs vs Greeklish Slugs