Commit 00fee8313844fe704257e017c8cef62ec8570921 enables file format support and it is mentioned in the release notes for 4.4 release. Though it doesn't work, neither importing or exporting works.
Testing with the Sep20 4.4.0 alpha git 1ee63d5)appimage confirms this. Opening: The file format cannot be parsed. Exporting: Error occured while writing to the file
From https://doc.qt.io/qt-5/qtimageformats-index.html > Note: For security reasons, the Direct Draw Surface (DDS) handler is not built by default since Qt 5.8. Users who still want this handler can build it from the source project. From https://forum.qt.io/topic/115239/how-to-display-dds-files/4 > As it stands right now, it's severely bugged and a security minefield (crashes). It is also pretty useless in combination with QImage: DDS files are supposed to carry multiple individual textures, texture arrays, cubemaps; mipmap chains; and may use specific texture compression formats. All these features are not supported at all by QImage.
This was disabled in 9d33bfba0f4e64ccde4902ddb91cb506f20111a4 on September 21s 2020. There are no plans to bring it back.