I've tried every possible constellation with either the embedded Python or a system-wide Python but I just can't package a game with the latest plugin version. I've also included an empty ue_site.py file like described in the readme.

My testscenario is a blank C++ project in UE 4.19.2 with the Python plugin.

This is my output log:

UATHelper: Packaging (Windows (64-bit)): ********** BUILD COMMAND STARTED **********
UATHelper: Packaging (Windows (64-bit)): Running: C:\Program Files\Epic Games\UE_4.19\Engine\Binaries\DotNET\UnrealBuildTool.exe tfbuildtest Win64 Development -Project=D:\ss\tfbuildtest.uproject D:\ss\tfbuildtest.uproject -NoUBTMakefiles -remoteini="D:\ss" -skipdeploy -noxge -generatemanifest -NoHotReload
UATHelper: Packaging (Windows (64-bit)): Using Embedded Python at: D:\ss\Plugins\UnrealEnginePython\ThirdParty\Python36
UATHelper: Packaging (Windows (64-bit)): full lib path: D:\ss\Plugins\UnrealEnginePython\ThirdParty\Python36\Lib\python36.lib
UATHelper: Packaging (Windows (64-bit)): Took 1.2170991s to run UnrealBuildTool.exe, ExitCode=0
UATHelper: Packaging (Windows (64-bit)): Running: C:\Program Files\Epic Games\UE_4.19\Engine\Binaries\DotNET\UnrealBuildTool.exe tfbuildtest Win64 Development -Project=D:\ss\tfbuildtest.uproject D:\ss\tfbuildtest.uproject -NoUBTMakefiles -remoteini="D:\ss" -skipdeploy -noxge -NoHotReload -ignorejunk
UATHelper: Packaging (Windows (64-bit)): Using Embedded Python at: D:\ss\Plugins\UnrealEnginePython\ThirdParty\Python36
UATHelper: Packaging (Windows (64-bit)): full lib path: D:\ss\Plugins\UnrealEnginePython\ThirdParty\Python36\Lib\python36.lib
UATHelper: Packaging (Windows (64-bit)): Parsing headers for tfbuildtest
UATHelper: Packaging (Windows (64-bit)): Running UnrealHeaderTool "D:\ss\tfbuildtest.uproject" "D:\ss\Intermediate\Build\Win64\tfbuildtest\Development\tfbuildtest.uhtmanifest" -LogCmds="loginit warning, logexit warning, logdatabase error" -Unattended -WarningsAsErrors -installed
UATHelper: Packaging (Windows (64-bit)): Reflection code generated for tfbuildtest in 7.2668511 seconds
UATHelper: Packaging (Windows (64-bit)): Performing 8 actions (4 in parallel)
UATHelper: Packaging (Windows (64-bit)): PCH.UnrealEnginePython.cpp
UATHelper: Packaging (Windows (64-bit)): d:\ss\plugins\unrealenginepython\source\unrealenginepython\private\Wrappers/UEPyFSoftSkinVertex.h(15): error C3646: 'ss_vertex': unknown override specifier
UATHelper: Packaging (Windows (64-bit)): d:\ss\plugins\unrealenginepython\source\unrealenginepython\private\Wrappers/UEPyFSoftSkinVertex.h(15): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
UATHelper: Packaging (Windows (64-bit)): d:\ss\plugins\unrealenginepython\source\unrealenginepython\private\Wrappers/UEPyFSoftSkinVertex.h(22): error C2065: 'FSoftSkinVertex': undeclared identifier
UATHelper: Packaging (Windows (64-bit)): ERROR: UBT ERROR: Failed to produce item: D:\ss\Plugins\UnrealEnginePython\Binaries\Win64\UE4-UnrealEnginePython.lib
PackagingResults: Error: UBT ERROR: Failed to produce item: D:\ss\Plugins\UnrealEnginePython\Binaries\Win64\UE4-UnrealEnginePython.lib

(I checked the ominous FSoftSkinVertex errors but couldn't detect any issues with that)

What am I doing wrong? Do I miss something?
Thank you very much in advance for the help!