This has appeared as a new optional dependency of sci-visualization/labplot.
I see a git tag, but couldn't find a source tarball anywhere yet.
FYI, source tarballs seem to be available now.
Created attachment 881693 [details] Draft ebuild Draft ebuild attached. I'm able to build other software against it on my system when installed, however, I had to stage the source tarball in my distfiles myself, manually. It seems Qt hasn't been uploading qtmqtt-everywhere-opensource-src-6.x.x.tar.xz files to their mirror since version 6. Apparently, they're aware of it: https://bugreports.qt.io/browse/QTBUG-113562.