I've been using Dell developer laptops with 4k+ screens and Linux for over five years. Haven't had any scaling issues either, since my external monitor is 4k as well.
There was also a story 5 days ago that putting an XPS in a bag voids its warranty unless it is completely powered off. Dell says you can't just close the lid to put the laptop in a sleep state before throwing it in your backpack:
https://news.ycombinator.com/item?id=28639952
(Of course, this could just be a CYA cover-your-ass clause that Dell's lawyers said to throw in to reduce lawsuit losses from lithium battery fires that affect all laptop makers including Apple. If the sales losses from this CYA clause's bad publicity are less than the reduction in lawsuit losses then I guess it's a win for Dell's balance sheet. I haven't seen any evidence that Dells are more prone to fires than any other brand.)
EDIT: I was just reading the linked XPS thread and it sounds like the overheating issue is due to a change in how sleep states were traditionally handled (S1/S3 etc.). This affects all Windows laptops, not just the XPS. A Linux XPS can actually avoid the issue if Linux sleep states are configured correctly, according to posters in the discussion.