I have just got Dell 3530 laptop, and they advertise an option to install second hard drive in WWAN slot. However, it has to be NVME (no SATA!) and it has to be 2230.
I have looked a lot, but the only NVME SSD in 2230 I was able to find was Toshiba BG3, but this one I can't find on sale anywhere. Do those exist beyond this elusive model, of "which everyone talks about and few have seen" (Quote from Francois de La Rochefoucauld)