I had this problem even with QT5.12. What fixed it for me was using my Nvidia graphics rather than my on-board graphics.
The "Qt5PrintSupport.dll" is present in bin for all QT5 builds, conda or otherwise.
However, the printsupport folder (child of bin), mentioned by @openbrain, from the French forum is not included in any build (well I added it to the libpack 12.1.2 0.19_pre builds).
I wonder if the OpenGL blackscreen in 3D view w/QT5 and this are related. When I have time I will switch to my on-board graphics and see if including the printsupport folder helps.
Anyway, no backport would be necessary to fix this, as it's all packaging related, I think.
PS: Everything on the releases page .7z, .exe, .dmg, .AppImage is a zip archive, you can examine the contents with for i.e. 7zip. Big downloads to just examine the contents of the packages, but I have more than a few .dmg's and AppImages on my Win machine for this purpose.
PS2: I can provide the printsupport sub-folder and contents (it's only 1 .dll) I prefer not to do it in the clear, because people will shot gun try it and may mess their system. PM me or better yet open a new thread and ask me to PM the necessary files.