Please do not report bugs to Looking Glass for any of the items listed here, they are not caused by Looking Glass and as such are out of scope.

I found X project/code that enables the NVIDIA Capture API for normal cards.

We really don't want to know about it, by using such code you will be breaking the NVIDIA Capture API License Agreement putting not just you but possibly this entire project in legal jeopardy. Making use of such code/applications is frowned upon and will not be supported in any way shape or form.

The agreement clearly states:

install, use and reproduce the software delivered by NVIDIA, make modifications and create derivative works of sample source code software delivered by NVIDIA and use documentation delivered by NVIDIA, provided that the software is executed only in NVIDIA GRID, Tesla or Quadro 2000+ hardware products that you separately obtain from NVIDIA or its affiliates, all to develop, test and service your products (each, a “Customer Product”) that are interoperable with NVIDIA GRID, Tesla or Quadro 2000+ hardware products

Please do not use, promote or distribute such code.

The mouse doesn't stay aligned with the host.

This is because of windows mouse acceleration, it can be disabled with the following registry magic:
Contrary to the title this works just fine on Windows 10

Qemu will crash on shutdown, restart or manual unloading of the ivshmem driver

This is a known problem that Ladi Prosek of Red Hat has been working to resolve, the following patch set correct this problem:

Mouse input freezes or stalls often requiring a reboot of the guest OS to recover.

Looking Glass uses relative mouse positioning for all movement, this is so that when using applications that require mouse capture (ie, FPS Games) the mouse behaves properly.

By default libvirt creates virtual machines with both a PS2 Mouse and a USB Tablet device, the USB Tablet device is used for absolute positioning. The libvirt virt-viewer application only ever uses absolute positioning mode and as such never triggers this bug in Qemu. It is possible however to trigger the bug in virt-viewer by removing the USB Tablet device from the guest, forcing it to use relative mode. This is a bug in the virtual i8042 controller in Qemu.

Attaching a virtual USB mouse to the guest doesn't resolve input issues either as once again, the relative input code has not been extensively tested. The USB mouse device has stalling problems likely due to virtual USB hub emulation problems.

These problems can be worked around to an extent by adding the VirtIO Keyboard to the guest and using the virtual PS2 mouse device, but it doesn't resolve it as the mouse is prone to lockup.

Alternatively you can pass through a physical USB controller and use a physical keyboard and mouse, or the use the evdev subsystem.

Audio isn't working

Looking Glass does not handle audio at all, if you're having audio problems please look to Qemu for help.

The Windows Logon Screen, Shutdown, UAC Dialogs, Ctrl+Alt+Del, LockScreen do not work.

These screens are on the "Secure Desktop", Microsoft has intentionally limited access to capture this screen to prevent malware attempting to capture information from these screens that might be sensitive. There is little we can do here unless Microsoft are willing to let us sign the host application as an 'Accessibility' program.

Users of NVIDIA cards that support the NVidia Capture API (Quadro, Tesla, etc) will find this limitation only applies to the Windows Logon Screen and Shutdown Screens, the NvFBC capture API is able to capture the "Secure Desktop" outside of Microsoft's control.

The Windows host program doesn't work as a service

As of Windows Vista, Microsoft deprecated the ability for services to interact with the user's desktop, and as of Windows 10 this is enforced. There is nothing we can do about this sorry.

NvFBC (NVIDIA Capture API) doesn't work

Unfortunately NVIDIA deemed fit to only allow owners of "Professional Cards", and their own software (ShadowPlay) the right to use the NVIDIA Capture API. There is little we can do about this other then to complain to NVIDIA.