Earlier quoted context omitted.
I was on the same boat and decided to install KDE Plasma. Very very happy with the result, the UI dark theme is very beautiful and all shortcuts and UI elements work the way "old" UIs did (unlike freaking Ubuntu 18 and 19 which changed everything for 0 reason). https://kde.org/plasma-desktop It was quite easy to install and everything worked out-of-the-box. I just customized some widgets, the dark theme, icon colors…
I've been on the brink of installing KDE many times over the years. What held me back was that screenshots always displayed bulky window decorations which I have no use for on a 13/14" notebook. Also, for space efficiency, I want global menus period. I think Ubuntu pre-18 with Unity got a lot of things right - a lean UI getting out of your way and yielding space to actual apps. I can do without the collection of desk…
Despite its bad reputation in early days, KDE Plasma 5 nowadays is very lightweight. As in, the resource usage is pretty much on par with Xfce.
[1]: https://userbase.kde.org/Plasma/How_to_create_a_Unity-like_l...