SUMMARY


STEPS TO REPRODUCE
1. Install kde-pim, kaccounts-providers.
2. Log in to NextCloud via Online Accounts in System Settings.
3. Go to Korganizer and add NextCloud calendar.
4. Configure Digital Clock widget in System Tray to show your Nextcloud calendar.

OBSERVED RESULT
Events do show up in the calendar view of that widget. However, every event is a different color. What's more concerning & the reason for my bug report: the color of the entire calendar changes unpredictably & frequently in Korganizer. Worse still and even more of a reason to file a bug: this unpredictable, frequent calendar color change affects all other devices with access to your calendar (On Linux, macOS, iOS, etc). These colors can be changed within Korganizer, but colors the user sets do not persist, even within the same session of use of Korganizer. The suggested workaround at: https://bbs.archlinux.org/viewtopic.php?id=300270 does not work.

EXPECTED RESULT
Calendar color coding that one has set for years, remains (eg. Calendar color you had set, doesn't change). If change is possible, necessary or preferable, there should be easily accessible and reliable controls to do so.

SOFTWARE/OS VERSIONS
Windows: (Have not attempted to use KDE or attempt Nextcloud calendar access from "The most open operating system" --Microsoft) 🤣
macOS: (not using KDE Plasma on such, but since mentioned above, 15.1.1. Also iOS 18.1.1)
(available in the Info Center app, or by running `kinfo` in a terminal window)
Linux/KDE Plasma: Arch Linux (rolling; current kernel 6.12.1-arch1-1)
KDE Plasma Version: 6.2.3
KDE Frameworks Version: 6.8.0
Qt Version: 6.8.0

ADDITIONAL INFORMATION
Added to above as it may be salient: Graphics session: Wayland (I have not attempted on X11)
I have perused discuss.kde.org & several other forums on the bug I'm experiencing, and the closest to a solution I got was the above bbs.archlinux.org workaround, which, as mentioned, doesn't work. I've read enough elsewhere to note that calendar color code changed from Plasma 5.27.x to 6.x, and seen discussions on users attempting to change colors in .qml code (at https://discuss.kde.org/t/custom-color-date-format-in-the-digitalclock-plasmoid-in-plasma-6-1/24296/14).
In my non-developer opinion (everyone has one, and I'll try to keep mine polite but salient), this is a suboptimal experience, particularly for any switchers from a different DE, or to Linux as a whole.
In fact, I may submit a separate bug wherein Dolphin file integration with Nextcloud only works once per entire system installation. If one ever needs to remove access to Nextcloud files, there is never a prompt to re-enter the password, should one want to re-add access. Kwallet/kwalletmanager don't help; they can remove the old password from the system; they cannot make Dolphin provide a new prompt; it just keeps telling the user they have no access to this resource.
Yes, the preceding paragraph of this "Additional Information" are on a completely separate bug, on a completely separate set of packages. That said, it does address the less-than-optimal state of overall UX for Nextcloud integration with KDE Plasma, hence its inclusion as a kind of "emotional barometer" for the user on the overall experience.