Unity’s global menu system was wonderful and once getting used to how well it used vertical space switching to gnome was like going back 10 years. Seeing multiple empty bars across the screen makes it completely unusable to me not to mention their need to replace simple menus with seemingly random icons scattered everywhere. I’m using kde plasma now with a global menu set up. It’s good but isn’t as hassle free as Uni…
Fortunately, there's a PR for implementing such things in KDE Plasma. Here is the discussion [1]. Right now, you can use it, but it probably won't be merged into the main branch soon.
PR: https://invent.kde.org/plasma/breeze/-/merge_requests/126
There's also a KDE theme the PR draws inspiration on (which you can use for KDE now): https://github.com/Zren/material-decoration