The laptop is DELL XPS 15 (9520); it has one 512GB SSD pre-installed, where the OS and apps are, and one empty M.2 slot. I am considering adding one more SSD to store media and files for data science. 1 or 2TB.
Both M.2 slots support 2230/2280 drives up to PCIe 4.0 x4 (source). I saw some...