If you wish to build Kirigami with Qt6, this is currently not possible with only distribution packages on Linux. You will need to resort to kdesrc-build instead.
Is this still relevant in this page given there are rolling release distros with KF6 packages like Arch?
This is only relevant if your distribution still uses Plasma 5, and you want to compile for Plasma 6.
Should I post an MR about this?
Sure. I’m about to merge a new guide explaining how to build with CMake and distribution packages manually, so we’ll need to update that section either way.