Recently I’ve gave up Windows for Linux and installed Ubuntu with KDE Plasma desktop on my pc and laptop from 2007. It’s an i7 Intel processor with 8gb ddr ram so I thought it would be fine, but it seems quite sluggish. What distro could I use that would be faster and still fully functional? Thanks for your help in advance.
You don’t really need to switch to a different distro. Just avoid snaps/flatpack/… and use a more lightweight desktop like XFCE and you should be fine.