HP OMEN: What can you retrofit?

Since my old laptop has given up the ghost, I want to buy a new one. This time it will be a gaming notebook from HP's OMEN series.

Since the notebook only has a 512 GB (m.2) SSD, I would like to add a second SSD later, as the capacity will not suffice. An additional HDD is not installed.

Oh, what am I talking about here? Here is the link to the notebook:

https://www.notebooksbilliger.de/...0ng+637500

Now I would like to know if anyone has had any experience with such notebooks.

As I have noticed, it should have a flap specially made for retrofitting, which makes retrofitting much easier.

Is that correct?

And which components exactly can be retrofitted?

LG and thanks for the answer!

RAM and SSD - just probably not without losing the manufacturer's warranty (if you do it yourself or place the order with an unauthorized dealer)