I say we add the nodirectwrite platform argument like we do altgr (except with no user preference involved) to force the gdi font backend for now. We can revisit removing it when the DirectWrite backend proves to be more complete.
If we don't do something, we'll be chasing mystery windows crashes as more users encounter embedded woff fonts on scaled displays. And I'm for the path of least Qt patching.
EDIT: for the record... adding the "fontengine=freetype" platform option seems to accomplish the same thing as nodirectwrite. It also eliminates any of the QWindowsFontDatabase::fontEngine warnings encountered when using nodirectwrite.