m15 R4, constant stuttering in Advanced Optimus or dGPU only modes

It sounds like you've done just about everything to try to fix it yourself. It is possible that the issue is also hardware related. Since you have only just received the laptop then you are best to contact Dell Support directly. You should see the Contact Support link on the right of your screen in the main screen under Dell Support Resources. 

You can try running the ePSA diagnostic, if you haven't already by pressing F12 during post to bring up the boot menu. This does not always find all hardware issues though. 

@kingsta1  This is a long shot, but after switching to Advanced Optimus or NVIDIA GPU only, try going into Device Manager, then disabling and re-enabling your Intel GPU.  I mention this because I have a laptop that has the external display outputs wired directly to the NVIDIA GPU, while the internal display is controlled by the Intel GPU, and I've found that if I transition from a state where the Intel GPU is active (built-in display on) to a state where the Intel GPU is no longer active (lid closed), then graphics on external displays controlled by the NVIDIA GPU become laggy.  This is noticeable even when scrolling webpages and such, but cycling the Intel GPU always resolves the issue.  If the system boots with the Intel GPU already inactive, that's fine.  The problem seems to be triggered by the Intel GPU transitioning from being active to inactive.  I have no idea what causes this or why cycling the Intel GPU fixes it, but it does.  I've now got a PowerShell script file on my desktop that performs this task so that I can quickly run it as needed.

Thank you - your long shot has resulted in a partial fix, in addition to me uninstalling a couple Windows updates (KB5000802 & KB4601319). The disable/re-enable routine had no impact until I removed these updates.

Weirdly enough - and I don't understand the logic here - the issue presents less often with Fast Boot disabled and as you suggest, disabling then re-enabling the iGPU clears things up until next time. I just had my first stutter-free game of War Thunder using dGPU only mode and G Sync (at last).

This is a hot mess though and basically negates any benefit of having Advanced Optimus.

I spoke too soon - the stuttering returned despite Windows Update being paused for 7 days and me having not installed any other software or updated any drivers. The disable/re-enable iGPU method didn't resolve it.

If I factory reset the laptop (third time now) and don't update Windows I can use FN+F7 as a MUX switch and when I reboot, this is true dGPU only mode with no iGPU visible in device manager. But the stuttering and micro stuttering is a problem. If this is broken out of the box and Windows/driver updates only make it worse then I'm leaning towards a hardware issue, perhaps heat related. I followed an undervolting tutorial for the m13 R4 on YouTube and that guy was getting c. 10c lower temperatures on several CPU cores and a smaller spread of temps between cores.

As soon as I update Windows the FN+F7 MUX switch no longer works, irrespective of whether I reinstall Alienware OSD etc.

Glad to hear my suggestion was at least a partial fix.  In terms of the Windows updates, unfortunately I'm not remotely surprised that Advanced Optimus is finicky at the moment.  It's a new a rather tricky bit of tech in a new system.  And I remember there was some Windows 10 release that started rolling out and was subsequently blocked from being offered to systems like mine that had dual GPUs with some displays wired to each GPU as opposed to a "pure" Optimus setup with everything run by the Intel GPU.  There was some bug that in the new release that caused it to break on systems like that.  This may be something similar.  I realize that doesn't provide a solution, especially in this era where Windows updates are increasingly difficult to resist.  All I can suggest there is to check frequently for driver, firmware, and OS updates.  I suspect there will be fairly frequently releases in the first two categories for a while if previous system model launches are any indication.

I'm having the same stuttering issues and fps drops with my 144 advanced optimus display on m15 r4 3060.

There's a recent Windows update that may cause stuttering in games (KB5001330) but I had these issues with or without that update installed, so you may be out of luck.

Sadly my laptop is being returned because I've been unable to find a solution despite spending dozens of hours on this. I decided it was a hardware issue in my case because GPU Z showed that in all games the stutters corresponded to a drop in GPU load down to <10%, with a VRel warning. This suggested to me that there's some sort of issue with the VRM, maybe thermal. I found that I got somewhat less stuttering with the laptop laid flat on a surface rather than propped to improve airflow, despite getting hotter temps. I can only think that the chassis is somehow flexing and the VRM heatsink and thermal pads aren't making proper contact. I didn't fancy opening up a brand new laptop to find out and Patrik at support recognised that I'd had a nightmare trying to get to the bottom of this, and we agreed a refund. I hope to order another but at the moment lead time is 60+ days which isn't encouraging.

If your issue is similar you'll likely see stuttering even in games that aren't pushing the GPU hard. I was seeing the same issues whether graphics were set to ultra or low, with the GPU load dropping from say c. 60% to <10% even when the thermals were fine (<70c GPU, <80c CPU).

Good luck and make sure you raise this with support so there's a ticket open and if you do require a return, you're inside the window and it will be less painful to sort out.

Disabling iGPU fixes the micro stuttering on the Alienware X17 R2, when connected external monitor through HDMI on a (hub) USB-C port. Alienware X17 R2 uses Intel Iris Xe as integrated VGA driver.I did not have this issue on the Alienware x17 R1 btw.
I end up disabling Advanced Optimus on bios and the Iris Xe as well. Leaving the graphics only to RTX 3080ti "solved" the problem.

I have the another model (G15 5520, i7, rtx 3060) and the same problems. Nothing helped and I was searching for answers. 

It was all because of my Bluetooth mouse. It made everything stutter a lot now and then even during normal work (only Chrome, photoshop was open). Now I have a cabled mouse connected and everything is running smoothly. I also checked the difference between turning on/off Optimus-Mode in Bios and after disconnecting th bt-mouse everything was fine for both.

For frogs sake.. I also thought it was a hardware problem and reduced all graphics down to minimum. Even Far Cry 6 was stuttering and it was the BT-Mouse the whole time ._.