I've confirmed this is an issue with another friend who has the same laptop.

Dell team, can you kindly confirm if the GPU works under load in Ubuntu 18 without performance jitters and crash due to thermal spikes (CPU and GPU)?

Performance on windows is also terrible. Games stutter and lag a lot. The GPU is virtually unusable for very light gaming. I noticed this is because of Intel Speed Shift. Disabling it in the bios gives good performance but the temperature spikes up (CPU and GPU) causing the laptop to crash.
Another issue I've noticed on linux is that while performance is good, temperature doesn't shoot up as much when the AC Adaptor is unplugged causing system to not crash/crash after increasing the load even more.
I'm pretty sure this is a bios issue. Waiting for Dell to release a bios fix at earliest, otherwise the GPU on this laptop is pretty much useless.

I'm having this exact same issue - @rraks, did you ever find a fix? I'm trying all sorts of combinations of thermald, i8kmon and throttled, but with no luck.

No luck.

Lost hope.

Support is unsupportive.

Hello!

I have the same problem, using nvidia performance mode, starting simple games on minimum designs, the laptop's off in five minutes.

Have you managed to solve the problem?