I use(d) the cachyos-emerald Plasma Style Theme. Went through an update this morning and when I rebooted after logging into desktop, it flashed black about 5 times and then stayed black with only the mouse showing on the black screen. I used a snapshot to go back prior to the update. Seen this in the logs:
Mar 02 12:39:50 cachyos-x8664 plasmashell[1615]: Could not find required file “mainscript” for package “/usr/share/plasma/plasmoids/org.kde.plasma.icontasks/” should be QList(“ui/main.qml”)
Mar 02 12:39:50 cachyos-x8664 plasmashell[1615]: The theme “cachyos-emerald” uses the legacy metadata.desktop.
Then I changed my Plasma style to Breeze, did the update, and it now works.
I am somewhat surprised there have not been more reports of issues earlier.
If we are finally at a point where it is causing breakage then it might be time for it to be removed from the repos if no one is going to take care of it and update it for current Plasma.
Like this is very old news and takes 30 seconds to ‘fix’ but no one has so .. maybe no one should be faced with this package.
So I still think it should be yanked from the repos if no one is going to take care of it.
EDIT.
Simply in order to demonstrate it I did the porting to the new format.
Give these versions a try (after unpacking you can place them in ~/.local/share/plasma/{desktoptheme,look-and-feel} & ~/.local/share/color-schemes as needed though I did not touch the colors).
As mentioned above this is simply your theme not being maintained.
I can do the basics of fixing the format but anything else that may need touching I would be unwilling to do unless its something extremely popular or that I use or something like that.
Actually .. upon looking at this it seems they actually made the correct json file but neglected to remove the desktop file .. possibly causing the deprecated one to be picked up.
$ git clone https://github.com/HimDek/Utterly-Round-Plasma-Style.git
$ cd Utterly-Round-Plasma-Style/desktoptheme/solid
$ ls
dialogs icons LICENSE.md metadata.desktop metadata.json opaque solid translucent weather widgets
But looking closer that json file is still a little broken.
Ok fine.
Here it is with format fixed. Again if anything more is needed then thats up to the theme dev.
We should really get packages like this one removed from Cachy. It is an official CachyOS Package that now breaks because of missing maintenance. That is bad PR.
I’ll flag this post for administration, maybe the Elder Gods will have a look at it.