Is there something like Ghost plugin system to extend core

I’m wondering if there’s any plugin system in place or in plans that allows extending the core? I imaging it should be similar to WordPress plugins.

You can do any code customization unless what you need is in this section :

He probably meant something that he can build. Not a third party plugin. Can I create for example comments for blogs where I store data in my database? How would I go about it. Basically add the web forms CRUD to the site without editing the core code?

Integration with Ghost is designed to be done via external services using it’s API and webhooks, this allows for extensions to be distributed/scalable and to have their own security contexts. There’s no direct comparison to WordPress’ “plugin” system.

There are also more and more services becoming available that let you take static sites and make them dynamic such as Netlify Functions or CloudFlare Workers, that’s also an option for building richer dynamic functionality.

Can I create for example comments for blogs where I store data in my database?

There are a number of commenting systems in the integrations directory and you may find more if you search on the forum, including ones which you can host yourself.

I see, thanks. I get the general idea. Not sure though that you can achieve deep customization with that approach, but I’ll keep this approach in mind when thinking about customization routes.