JT Event Calendar (version 8.1.0 or greater) is compatible with Gutenberg editor.
In order to convert the old event's info and tickets section to Gutenberg's content blocks, you have to add the following filter in your theme's functions.php file.
Now, go to an event's edit page and make sure that your content is there. If it is, then remove the line you added in your theme's functions.php file and you are ready to keep adding/editing events using Gutenberg editor.
After that, you can add the available Gutenberg blocks for JT Event Calendar and display your event's info using the brand new Gutenberg styles for events' single page styles. Otherwise, you can still use the old single event page styles.