To make the plugins fail to allocate if the image size is greater than QImageReader::allocationLimit() it is necessary to allocate the image with QImageIOHandler::allocateImage().
Note that not all plugins have been changed and some others are not tested in the CI (maybe due to missing libraries).
PS: the following message is printed by QImageIOHandler::allocateImage() if the size is exceeded: "qt.gui.imageio: QImageIOHandler: Rejecting image as it exceeds the current allocation limit of XXX megabytes"
New libjxl API changed the way how lossless 16bit depth images
must be encoded: codestream level 10 must be set,
which implies use of container format.
Unfortunately, there isn’t version number inside libjxl header yet,
so we must detect new version on cmake/PkgConfig level.