The windeployqt tool does not seem to correctly identify the required DLLs for projects built using Visual Studio 2019 (specifically using the v142 toolset). For debug builds, it copies some release DLLs (qwindows.dll instead of qwindowsd.dll), and it fails to copy some debug DLLs because it is looking for a file with 2 post-fixed d's.
I am not using qmake. The project is configured with CMake. I have tried using both the Visual Studio 16 - 2019 and Ninja CMake generators. It doesn't seem to matter if I target x64 or Win32.
My current workaround is to go back to the v141 toolset. This can be installed separately from within Visual Studio 2019.
I can post a simple example project to Github that exposes the problem if there isn't enough info here to replicate it.