Drupal form creating method without using a module

I am working on a Drupal site and it has a custom form in the frontend. I want to remove that form, but the problem is it is not generated by a custom module.

There is only one custom module. so I disabled it to check if that's the module generating the form. I cleared the cache also.

But the form is still there. So is there any other method of adding a form to a Drupal site without using a custom module?

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