Hi @patrick797, and welcome!
The slow-ness can be caused by misconfigurations, as well as hardware. Considering you tried Fedora and Solus as well and it’s the same with them, it points to hardware. Quite possibly old/insufficient hardware.
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Also, you might benefit from a more lightweight desktop environment, seeing as KDE is quite resource hungry. Try Xfce (although I’ve heard it uses quite a lot nowadays, it might still make a difference) or Lxqt