There's a bug when changing Wallpaper Plugin. Left Clicking to open the ComboBox's drop down menu, then left clicking a different plugin will not switch the GUI. Scrolling over the ComboBox works though.
There was a Kirigami.FormLayout + QtQuickControl2 patch that changed QtControls1.ComboBox.onCurrentIndexChanged
I also noticed the CombBox no longer updates when a wallpaper plugin is installed which https://phabricator.kde.org/D15178 added.
The "Layout: Folder View" => "Layout: Desktop" ComboBox also displays this bug.
The Image wallpaper plugin's "Scaled and Cropped" ComboBox is still using QtQuickControl1.onCurrentIndexChanged so it does not have this bug.
Neon's gitunstable ISO has Qt 5.11.2
There was a bug in QQC2 combobox with the desktop theme. Should be fixed.
581b140c8b81096f40ddebd84b8b2fbc327b616d in qqc2-desktop-style.
I can confirm that Neon's
is using `model` on line 72 + 210 instead of `delegateModel`.
After modifying the file and restarting plasmashell, the bug was fixed. :)