Welp, this is a weird one, but I tempted fate by putting my FG project down (just for a couple of weeks!) and when I went to pick it back up again, bitrot has set in and now nothing works!
It's probably something I did, but heck if I can remember doing anything that would have screwed things up this bad. I'm running a custom Windows build that I created via the fg-from-scratch process, and the symptom I'm seeing is four windows popping up reporting DLL errors: The procedure entry point could not be located. The affected files are all in Qt: Qt5Qml.dll, Qt5Quick.dll, Qt5QmlModels.dll, and one in fgfs.exe.
This was all running fine before and I have not even recompiled the project since the last time it ran, so I am very confused. The only things I can think of are a Windows update sabotaging me somehow, or else something else I installed caused a change in path or something? I only have the one version of Qt, which I've been using the whole time, so I don't see how it could be a wrong Qt version problem.
The only significant work I was doing while I wasn't playing with FlightGear was working with Lidar scans using CloudCompare, Meshlab, and Blender, maybe something in there changed my underlying software architecture?
Any suggestions would be welcome, I am quite perplexed.