AUR is reposnsible for the vast majority of -Syu into softbricks, and is little better than downloading random binaries (because you literally are most of the time)
I would advise taking either fedora or Mint KDE spins. The KDE 6 update was hard scuffed on Neon, and I take that as pretty strong evidence that their test infrastructure is not mature enough.
This sort of event would be totally unacceptable to me on a system I needed to use.
Linux.