Although its high-end variant is also available in black — unlike the XPS 15 9570 laptop — and features an 8th generation Intel Core i7-8705G processor, the XPS 15 9575 convertible only comes with 16 GB of soldered memory, so there is no upgrade option available. Fortunately, Frank Azor has just confirmed that a 32 GB variant should arrive in the last part of the year.
https://www.notebookcheck.net/Frank-Azor-The-Dell-XPS-15-9575-convertible-with-32-GB-RAM-coming-in-Q4-2018.306118.0.html