Finally have some breathing space after a busy week, so to unwind in geek-like fashion, I stayed up late last night and installed KDE-Standard and Kvantum onto one of my real metal MX19 installs for the first time.
Then I did some exploration into the world of Plasma customisation, because I'd never really got into it. I've had KDE Neon and Sabayon KDE on my multiboot machine for maybe 4 years now but have not done much tweaking. When "blur" became a Plasma feature, I did make my own adjustments to Desktop Effects and Konsole's settings to get some transparency blur but without applying a full set of customised themes, the blur look won't be shown off to maximum effect.
Previously, I'd kept mainly to Breeze Dark (with different colour schemes) or the Kvantum version of very standard themes like Arc Dark and Adapta Nokto, and a few early "blurred look" kvantum themes. Found a few window decorations with a "glassy" look to go with the blurred effect. Tested a few SDDM themes and found them a little buggy (can't get the reboot/shutdown controls on login screen to work). After that I hadn't bothered to check out Plasma customisation for more than a year.
I was aware of how much Plasma could be dressed up though, through the screenshots threads in Manjaro forums. So last night I checked out newer themes for SDDM, desktop, window decorations, and applications (ie kvantum styles).
There are very nice ones that make full use of the blur effect.
https://imgur.com/1Bruw7J
This is mainly the Cleaia theme for Plasma Desktop, window decoration, colour scheme and kvantum.
KDE Splash Screen - Sweet theme
SDDM - Monochrome theme. Different SDDM theme from what I used in Neon, but again the shutdown/reboot controls don't work. I suspect it's a Plasma 5.14 bug because Neon is now running Plasma 5.18 and the newer sddm themes I tested yesterday are now able to use those controls.
Unfortunately Debian Buster's Plasma 5.14 is too old to utilise those newer SDDM themes like Cleaia, Sweet, Ant-Dracula, Ambient-Blue or Layan.
The options for customisation in Plasma are endless and I've hardly scratched the surface. E.g. you can reconfigure the layout for Dolphin, make the desktop look more like other DEs, install a Unity-like HUD, etc etc. However I'm not interested enough to explore further.