Possibly relevant article from April, 2019
https://www.xda-developers.com/nvidia-desktop-experience-shield-tablet-2019/
"Mystique”
"According to code we examined within the latest SHIELD Experience software, a new desktop-mode software feature is in-development for a new product code-named “mystique.” Furthermore, source code published online by NVIDIA reveals some possible hardware specifications for “mystique,” suggesting it could be a 2-in-1 PC like the Microsoft Surface Book. "
".. code from the SHIELD TV’s latest software releases points to a new software feature code-named “NvDtExp,” likely short for NVIDIA Desktop Experience. This software feature is almost certainly not intended for the existing SHIELD TV products. It is also highly unlikely for NVIDIA to upgrade its existing tablets with this feature, given that it’s been over a year since they last released an update for the SHIELD Tablet K1. Lastly, the code makes many references to the product code-named “mystique,” which suggest the new feature is intended for this new product."
"The code was first discovered by a custom ROM developer who shared his findings with
XDA-Developers. We confirmed the presence of this code, which seems to handle the switching between UI modes for NVIDIA Desktop Experience, in production builds of SHIELD Experience dating back to December of 2018 and continuing into the latest SHIELD Experience 7.2.3 release from last month. Although
SHIELD Experience 7.2 was the first release containing the desktop mode switcher code, we suspect that NVIDIA has developed this feature for months before its first appearance in a public release."
"From the code, we can confirm several details about the SHIELD Desktop Experience feature. First, there are 3 supported UI modes: Dynamic, Tablet, and Desktop."
"There are mentions of start menu visibility and mouse hover control for the desktop UI mode. Other aspects of SHIELD Desktop Experience that we see in the current firmware include the ability to set a UI mode on boot, start desktop mode if a keyboard is attached, and intercept certain button combinations to show the status bar, show the power menu dialog, close active windows, or toggle full-screen mode."
"The “mystique” code-name fits NVIDIA’s pattern of using Marvel character names. For instance, the SHIELD Portable was originally code-named “thor,” though it was later changed to “roth.” “WX,” or Weapon X, and “SB,” or Songbird, have also been used in the past. On the TV front, we’ve seen code-names like “blake,” “jarvis,” “pepper,” “thunderstrike,” “darcy,” and “foster.” Thus, spotting “mystique” in public source code is what first tipped us off about the possibility that it’s an in-development product, but it was our discovery of the SHIELD Desktop Experience feature that really connected the dots. "
"At one point, NVIDIA was developing “mystique” with the Tegra X2 (t186), but more recent commits showed “mystique” in the device tree for the Tegra Xavier (t194.) The Tegra Xavier is a large, high-performance chip intended for automotive and AI computing, as seen on the
Jetson AGX Xavier module released in late 2018. The Jetson can operate at a lower 10W power profile compared to a maximum 30W, so likewise “mystique” will be running at lower power, if it is indeed powered by the Xavier SoC. In contrast, the SHIELD Tablet K1 is powered by the 2014 Tegra K1 while the canceled 2016 SHIELD Tablet, code-named “hawkeye,” was expected to launch with the Tegra X1 like the Nintendo Switch and SHIELD Android TV. Having the Tegra Xavier would make “mystique” NVIDIA’s most powerful consumer product, but again, we have to stress our uncertainty in our knowledge of its hardware specifications given that the code we spotted may not reflect the current status of the product."
https://www.xda-developers.com/files/2020/04/Tegra-Xavier-Overview.jpg