This bug seems still to exist.
$ sudo emerge ksysguard -v These are the packages that would be merged, in order: Calculating dependencies... done! emerge: there are no ebuilds to satisfy "sys-apps/lm-sensors:=". (dependency required by "kde-plasma/ksysguard-5.20.5::kde-kit[lm-sensors]" [ebuild]) (dependency required by "ksysguard" [argument])