The latest KDE image available for ISO download from manjaro.org appears to be broken. I couldn’t install it at all in the first instance on a system on an NVIDIA PRIME integrated-dedicated switching system, as mhwd just hung indefinitely in Calamares. After I manually disabled mhwd in Calamares and installed it, though, the kernel manager immediately told me my kernel version was unsupported. I switched back to the LTS kernel rather than updating, as is my wont, but it’s probably not great for newbies.
A new build might be a good idea - I don’t know whether the PRIME issue was linked to the kernel version, but I have my suspicions