Sadly I am not using BTRFS for my root directory on this specific system. If I end up deciding to reinstall, I will definitely go back to BTRFS to avoid such problems.

Debian actually has a KDE group named kde-full. I reinstalled it but the issue persists, which was honestly surprising to me.

~$ sudo apt install kde-full
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
kde-full is already the newest version (5:147).
0 upgraded, 0 newly installed, 0 to remove and 87 not upgraded.

The new user idea was really clever, thanks for the suggestion! I will try that now and see.

Edit: the new user also presents the same problem. Actually, it makes sense, since SDDM is affected as well (I should have mentioned that before).

I do store regular backups of this machine, but not of /var. I can always reinstall Debian (or whatever other distro), while keeping other relevant configs intact (stored in the backups) and not lose any critical data.

I commented below that I did check /var/log/dpkg.log, but it didn't help much due to the high number of packages removed that day.

At this point I am more curious to learn more about KDE and what is causing the problem, since other desktop environments (I installed mate) seem to work fine.

Yeah, I tried installing kde-full but it didn't solve my problem.

You are right, I should have made this clear. I am not on Nvidia, I am using an old Thinkpad on Intel Haswell.

I'm glad to know my problem isn't completely new. I'll look into it further online. If you ever find a link to a report of a similar issue, I would be happy to see!

Edit: I found this link, the issue reported appears to be very similar to what I'm seeing here https://libreddit.tux.pizza/r/kde/comments/jhqbnz/kde_plasma_rendering_problem_black_squares/

Edit 2: I finally solved my problem! It was indeed an old problem already reported somewhere.

Haha, yes, I'm glad they chose not to!

The Gentoo sub had such a nice subtitle because it is indeed accurate! Definitely one of the things I like the most about "flexible" distros.

"Gentoo Linux: Because you like it when the power is in your hands"

I had to use both since I don't own a nice camera or lenses. I think exposure time was around 6 seconds. If you darken it by 2EV, it should be close to how it looked to the naked eye

Indeed it looks like a bug. I finally found a solution, though. Check the main post edit for details.

I audibly laughed at this. I actually knew I was entering treacherous waters by running apt full-upgrade in Sid, but still thought "well, we'll see..."

Thanks! Some packages were installed, but it didn't solve it yet (even after a reboot).

...
Install: orca:amd64 (46.0-1, automatic), libpcaudio0:amd64 (1.2-2+b2, automatic), speech-dispatcher-audio-plugins:amd64 (0.11.5-4, automatic), python3-brlapi:amd64 (6.6-5, automatic), xbrlapi:amd64 (6.6-5, automatic), speech-dispatcher-espeak-ng:amd64 (0.11.5-4, automatic), libsonic0:amd64 (0.2.0-13, automatic), sound-icons:amd64 (0.1-8, automatic), python3-speechd:amd64 (0.11.5-4, automatic), libespeak-ng1:amd64 (1.51+dfsg-12, automatic), python3-louis:amd64 (3.29.0-1, automatic), x11-session-utils:amd64 (7.7+6+b1, automatic), xkbset:amd64 (0.8-1, automatic), task-desktop:amd64 (3.75, automatic), libdotconf0:amd64 (1.3-0.3+b1, automatic), xorg:amd64 (1:7.7+23, automatic), perl-tk:amd64 (1:804.036+dfsg1-2+b1, automatic), x11-apps:amd64 (7.7+11+b1, automatic), speech-dispatcher:amd64 (0.11.5-4, automatic), espeak-ng-data:amd64 (1.51+dfsg-12, automatic), task-kde-desktop:amd64 (3.75), xinit:amd64 (1.4.2-1, automatic)
End-Date: 2024-03-26  17:42:41

If I am not mistaken, I used a Debian KDE live image from the official repository then switched the mirrors from Bookworm to Sid. The system went months without a single issue, then this happen.

Your suggestion will actually be my solution of choice if everything else fails: reinstall / and import relevant files from a backup that I already have.

Gorgeous view!

Thanks for the tip! However, I tried apt reinstall kde-full and apt --fix-broken install, but no packages were installed and (unsurprisingly) the problem still persists.

Tasksel seems to be correctly set,

~$ tasksel --list-tasks
i desktop       Debian desktop environment
u gnome-desktop GNOME
u xfce-desktop  Xfce
u gnome-flashback-desktop       GNOME Flashback
i kde-desktop   KDE Plasma
u cinnamon-desktop      Cinnamon
u mate-desktop  MATE
u lxde-desktop  LXDE
u lxqt-desktop  LXQt
u web-server    web server
u ssh-server    SSH server
i laptop        laptop

I tried apt reinstall kde-full, but unfortunately nothing changed.

Thanks for the recommendation! I will definitely do it when I eventually install some other distro in the future.

Haha, now I can't unsee it! I guess the whole thing was more obvious in person.

I tried reinstalling kde-full, but sadly nothing happened (all packages were already marked as installed).

I agree with that. I suspect you might be right. SDDM (Breeze) is also weird with transparency. However, I just installed materia-kde but unfortunately the problem persisted (screenshot attached). Before that, I ran apt purge kde* plasma* libkf* and apt install kde-full. That too didn't solve my problem.

You are absolutely right. I just tried apt purge kde* plasma* libkf* and apt install kde-full followed by a reboot. But sadly, the problem persists.

I did check it, yes, but the page doesn't appear to be relevant or contain much information. Another comment above (or below) mentioned that KDE Plasma can't run without a compositor.

I will very likely migrate to BTRFS on my next install. I'm reading Snapora's repo now, looks like an awesome tool. Thanks for the tip!

Yes, fully open aperture, long exposure (6"), and high ISO. I tried to recover the yellows that were (much) more apparent to the naked eye, and this made it look more saturated