from the AUR. But apparently the packages have been dropped. From the maintainer:
I'll drop this package, I been thinking and there are a lot of strong reasons not to waste any time maintaining it.
KDE doesn't provide an easy way to download the entire Qt source code in a single package, like in the official Qt releases.
Also, KDE doesn't provides tagged versions, I've to keep tracking manually the latest commits, or converting it to a git package.
It will require to split this package into 47x4 packages, 47 Qt modules and 4 architectures to maintain, that's 188 packages to maintain, absurd!
Cloning a git repository is slower than just downloading a source package file, making the build even much slower and painful.
Is a lot of work for something that will be dead in 1 year or 2 at most.
Good luck to the one that will step up to take care of this monstrosity, to the rest of developers, don't be lazy and consider switching to Qt6.
Which leaves me with the only alternative being to use the Qt Online Installer. I guess this must be the only option. Which is a bummer, because now I'll have duplicate packages on my system.