On System Settings Version 4.97.0 Using KDE Frameworks 4.100.0 I cannot find the option to set the date from my default to my preferred (YYYY-MM-DD). I am sure I could change the region, but I would prefer it to remain the same. Reproducible: Always
Does changing the format in System Settings > Locale > Date & Time work?
Ah wait, this is about the KF5 based version, yes, I think Qt does not support it yet.
Yes, this is currently unsupported in Qt5 / KF5 / Plasma Next. It will come back though (it's the first thing I change), it's just one of those features that needs more work in Qt5 before we turn it back on.
Discussion moved to bug 340982. *** This bug has been marked as a duplicate of bug 340982 ***