I find that setting the power profile to “Power-Saver” makes a huge difference.
KDE has support for that built-in, although I’m not sure, if distributions install the corresponding daemon on desktop systems: https://gitlab.freedesktop.org/upower/power-profiles-daemon
You should be able to cycle through power profiles with Meta+B on KDE.
You can also see and change the profile via the systray icon for the battery, but on a desktop system, that presumably won’t be shown by default.
Otherwise, powerprofilesctl is also an option, as described in that link.



















Yeah, it should come with the next Fedora release, which is scheduled for October 20th.
Feature updates, like this new Plasma version, get shipped every half year on Fedora. In between, you mostly just get security and bug fixes…