SUMMARY Plasma does not the Hebrew Noto Sans fallback font in Kubuntu, it uses Liberation Sans instead. OBSERVED RESULT Plasma uses Liberation Sans as the fallback font for Hebrew. EXPECTED RESULT Plasma should use Noto Sans Hebrew as the fallback font for Hebrew. ADDITIONAL INFORMATION The selected display font is Noto Sans. This problem may should be reported to Kubuntu, but I could not report to their bug system.
This is something controlled by the fontconfig file, which comes from the distro, not from KDE. You will need to report this to the Kubuntu folks, yeah. :)