Hi, It's been mentioned a few times already over the past, but we have been working on a new UI for KSysGuard over the past year. With landing most of the base work for Plasma 5.19 the new UI has been split to its own repo and can be found at https://invent.kde.org/ahiemstra/ksysguardqml .
The long term the plan is to replace the current KSysGuard UI with this new UI, but I don't know yet for what version we will do that. Right now we are working on polishing some of the UI elements as well as performance improvements to the page editing UI. Cheers, Arjen