How to make a Product Detail mandatory in Leads

Hi Community,

I am trying to implement a requirement in the Lead Section where the Product Detail (list) must be mandatory. If the list is empty, the user should be prevented from saving the Lead or moving forward.

I am trying to achieve this via Business Processes/Business Rules.

What I've tried: I attempted a Business Process triggered by a Lead Signal to show a dialogue box/Pre-configured page.

My Questions:

1. Is there a way to use Business Rules to validate if a Detail (List) has at least one record?
2. Is there a "Pro" no-code workaround to block the "Save" button if the product list is empty?

Any advice on the best architecture for this (DCM vs. Process vs. Hidden Validation Fields) would be greatly appreciated!