There’s also Ubik by Philip K. Dick where the recently deceased are able to communicate with the living AND aside from that also advertise a product.

I looked it up. Ubik was written earlier in 1969, than Neuromancer, which was written in 1984

Haven't read Ubik. I'm under the impression it essentially happens by magic (fantasy)? Or is some fictional technology involved?

It is a kind of cryogenic technology where the person is “half-alive”. But still I guess the book itself does have magical elements in it such as psychic powers.