XPS 9570 Disable internal GPU but still use external monitors cinnected via a dock

What are you referring to as the "external GPU"?  The only way to have an external GPU is with an eGPU box like a Razer Core X, or a similar Thunderbolt eGPU box.

If you're referring to the Intel GPU and nVidia GPUs as internal and external then no, you cannot go what you want to do -- the system is wired to pass all GPU data through the Intel GPU on its way to the display device, whether that's internal or external.

Sorry for the unclear wording. You correctly interpreted what i meant with internal/external.

Internal : inside the Processor, the intel GPU

External : external to the Processor, the NVidia GPU

When i disable the Intel GPU the notebook display will still work just the ones connected via the dock aren't working. So that everything goes through the Intel GPU seems not to be completely correct. 

> There may be only a partial-disable for the internal display for safety reasons (were you to disable it completely, you'd have no display at all).

Sounds valid and fits to my observation.

Presumably one of the IT problems where to many parties are involved (Dell, Microsoft, NVidia) To hope fo ra solution

You have the answer regarding the dock --- it's no, since disabling the Intel GPU disables the external display.

And as far as I am aware, the system is MUXless - it uses the Intel GPU as primary at all times, internal and external.  There may be only a partial-disable for the internal display for safety reasons (were you to disable it completely, you'd have no display at all).

The only Dell systems of recent vintage with the ability to control the display output on a GPU level are the XPS 9700 with the RTX GPU, a couple of Alienware systems with high-end GPUs, and the 7000-series Precision models.  Everything else is MUXless, with software control only.

The solution is an external GPU, but at the present time, that may not be practical unless you have unlimited patience (decent GPUs are all on allocation, often being sold by lottery) and funds (the prices are astronomical; the system I'm typing on has an RX580 GPU that cost me $200 in 2017 -- it's $800 in 2021).

@Ralf Jansen  The answers from ejn63 are correct.  On the XPS 15 9570, all outputs are wired to the Intel GPU, and therefore it must remain active for any displays to display any signal.  The NVIDIA GPU when active works as a render-only device using technology called NVIDIA Optimus, but even then it has to pass video frames over to the Intel GPU so that it can pass them through to the displays.  There is no way to have the NVIDIA GPU take direct control of the outputs in that system.  Some systems have outputs directly wired to the NVIDIA GPU, and a few systems have a BIOS option allowing you to customize which GPU controls the outputs because they have a more complex motherboard design that allows that flexibility, but that is not how the XPS 15 9570 works.

What you CAN try is going into NVIDIA Control Panel and creating an application profile that specifies that the NVIDIA GPU should always be used for that application, rather than using the default automatic decision.  But if that doesn't work either, then I agree you'd either have to hope this improves with driver updates or look at a true external GPU, but that would indeed be somewhat expensive right now.  But if you went that route, you could connect the eGPU to the Thunderbolt port on your dock for convenience.  Some eGPU enclosures offer docking station type of functionality like USB ports and Ethernet, but they won't provide enough power to run the XPS 15 properly because it's designed for 130W, which is above the USB PD max of 100W.  Dell did something proprietary to support running 130W over USB-C/TB3, and the WD19TB can do that, but third-party peripherals won't be able to.  So if you wanted to connect the eGPU directly, then you would also want to connect the system's own 130W power source to the barrel-style power connector, otherwise you might see performance throttling.  That's especially true because the XPS 15 9570 will only draw 65W from third-party USB-C power sources, even if they support providing more, which means the eGPU enclosure would only be able to provide half of the power the XPS 15 was designed to have available.

And just for future reference, the clearer terminology for GPUs is "integrated" (Intel) and "discrete" (internal NVIDIA).  If you say "external GPU", very few people will assume you mean "external to the Intel CPU".

Thanks for confirming.

The nvidia control panel is pretty useless in a current Windows 10 (the control panel also says so and points you to the windows settings). Windows does it now in the advanced graphics settings itself  and you can even select the "Windows Display Manager" ("dwm.exe") to render on the discrete gpu. But somehow it does not work. The apps i configure there do actually render on the discrete GPU but since most of the rendering is done by the Display Manager (and that one seem to ignore the settings and renders on the integrated GPU) it does not have any positive effect. 

The application i struggle the most with is Microsoft Teams and trusting the taskmanager it renders almost anything via the Display Manager. That goes into the direction of more of a Microsoft/Windows Problem so i will try the Microsoft support.