We'll create fresh WordPress site with REST API support for Crayon Syntax Highlighter installed. You have 20 minutes to test the plugin after that site we'll be deleted.
Crayon Syntax Highlighter is one of the best code syntax highlighter plugins for WordPress and currently it does nto support REST API. This means that it does not highlight code in posts created via REST API, including posts created by Gutenberg.
This plugin adds support for it.
No more plain code!