Slackware 14+-current KDE5 on my desktop suddenly has broken/blank/nonexistent (Plastik) window decorations. I did 'slackpkg reinstall kwin,' even 'slackpkg reinstall ktown' a few/couple times each (downloading & reinstalling completed)... of course also did 'slackpkg update,' 'slackpkg upgrade-all' (no related packages) but nothing changed. I will be upgrading/overhauling/replacing this desktop next week, so this isn't that big of an issue. If anyone has an idea to debug, I would try it... but I think it's another of dozens of cases of KDE configuration gone wrong from normal usage...

Clarification: the viewinder/crosshairs in attached image is part of a basic X pointer set I made years ago (with kolourpaint & gursor maker?)... it's incomplete, but I'd share it. I got tired of Apple-/Windows-style cursor active area being top left of pointer. Mine is in the middle (and you can even see the middle pixel colour if not too new monitor ('retina.')) There isn't anything else much different with that X mouse pointer set other than the 'waiting' icons are like analog (circular) clocks (some pointers will drop back to default like some included X alternative sets do)...

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I think could be something connected with the -current's upgrade of Qt5 from 5.13.2 to 5.15.0

From what I read, the Plasma5 releases are supposed to be used with certain Qt5 versions.

Apparently, the latest Plasma5 stable release is supposed to work with Qt5 5.12.x and 5.13.x

Then, I suggest you to rollback to previous Qt5 package from -current, which was 5.13.2

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It was something connected with the -current's upgrade of Qt5 from 5.13.2 to 5.15.0. I did a rollback to previous Qt5 package from -current, which was 5.13.2. Now Plastik returned.

I don't have any of these problems with Slackware64-current and the latest ktown.

KDE Plasma Version: 5.18.5
KDE Frameworks Version: 5.70.0
Qt Version: 5.15.0
Kernel Version: 5.4.44

I noted this:
I don't see a 'slackpkg install ktown' or slackpkg clean-system. Based on your above commands I am assuming you are using the slackpkg+ extension to slackpkg.

This puzzles me. Why deviate from the standard location? Can't help but wonder if perhaps this is related to your problems.

While I was writing my last post I decided to give this Plastik Widows Decorations a try. It does come up empty at first look, clicking again on "Windows Decorations" or clicking on "Application Style" then back on "Windows Decorations" in shows. I've been using it for the last 7 hours.

Hmm... I see there has been some editing to the original post. The two excerpts I quoted in my post above are no longer there.

I can confirm the plastik window decoration theme is currently broken. I rather preferred it over the over simplified flat look of the default.
While switching to a different theme and back will temporarily fix it, it will be broken again the next time you login.

After some more updates, it happened again (selecting it re-shows it only in KDE settings, but it won't show up on any program.) Rolling back QT5 just breaks Konsole.

My

I've been using the Plastik theme for two days now, don't see any issues. Forgot to switch it back to Breeze.

I think this is a bug with Settings. When selecting "Application Style" from "Appearance", after entering "Application Style" the item "Application Style" is selected (highlighted dark blue), the "Windows Decorations" is also selected/highlighted with light blue. Selecting "Application Style" clears the light blue from the "Widows Decorations" item. Then after selecting "Windows Decorations" the Plastik theme is visible.

At any rate, this is more of a glitch or bug, the theme it self seems to works just fine. I would hardly call that broke.

Since QT5 is part of Slackware now, I'm guessing this will remain solved (as it is sometime before update.)