Thanks for your help! Launching the editor via Visual Studio debugging (with C++ and win32 exceptions checked) didn’t reveal much more about the call stack, and then as a control-sample I made an identical (new & empty) project in UE4.24, debugged it the same way, and when the editor creates a file-explorer window, the exact same errors came up, same call stack (then a couple more errors) all with no crash. So my call stack seems to be a red herring and Unreal / Visual Studio might not be logging what actually causes the crash.
I’m feeling pretty stumped at this point. I might have to just hope there’s a hotfix coming soon. (Though I still don’t see this error in the buglist yet despite multiple reports days ago, so I wonder if it doesn’t repro on their machines.)