Really having an issue with this one.

As others have mentioned, some machines may have supported both.

There’s an almost gaurantee that the board used only DDR3L. DDR4 wasn’t mass produced until mid 2016; a year later than this laptop.

The DDR4 slots look like the attachment joints were soldered after market, because they appear to have exposed copper or gold. Pretty certain the joints should be covered in tin solder.

What’s the story on this board/laptop? Are you a potential buyer?

YouTube search for reset winsock.

Mdtechvideos explains it well.