Install RAM in Dell XPS 15 9550 or 9560 Kaby Lake Upgrade - YouTube
Unfortunately, the XPS 15 9575 2-in-1 has soldered RAM - NotebookCheck.net News
Dell XPS 15 9510 gets a 3.5K OLED touch option along with ray tracing and DLSS support thanks to RTX 3050 and RTX 3050 Ti Laptop GPUs - NotebookCheck.net News