How to create a subcategory to a PAGE on WP?

There is very simple way to do this:

  1. Make a page with slug ‘lp’ or whatever you want

  2. Then create page with slug ‘banana’ and set the previously created page ‘lp’ as it’s parent from the parent dropdown list.

  3. Do the same process for other pages whom you want to display like ‘lp/otherpages’

You can also add category support for pages via coding but I think the above points will solve your problem.