Importing a product catalog from another site - is it possible? How to do it better?

Question

Search Engine Optimization

The customer asked to upload a catalog of electrical goods to his new website.
We will download from the dealer site - there is an agreement, we do not steal.

But what about SEO?
A new online store filled with goods downloaded from another site - how will Yandex, Google react to this?
What can be done and should anything be done at all?
Some SEOs say that news and products can be easily copy-pasted without compromising SEO - they say PS are not sensitive to this type of content - anyway, everyone copies goods from each other.

Where is the truth? What's the best way to do it? Is it possible to synonymize or somehow dilute (uniqueize) texts with something?