Ghostwriter doesn't compose the window on Plasma/X11

[elegos]

Hello,

I'm running Fedora 34 with KDE Plasma (framework 5.85.0). I've noticed that unfortunately Ghostwriter simply won't render on X11 ("transparent" window with stuck background image moving the window). It works though on Wayland, even if it's not an option, at least for me, due to the series of artifacts I get with my nVidia graphic card (i.e. no transparency, black areas etc).

If I try to run Ghostwriter via a terminal, the following message keeps repeating, which I think it's the source of the problem:

Using pandoc version 2.9.2.1
Using multimarkdown version 6.6.0
Using cmark version 0.29.0
qt.qpa.backingstore: composeAndFlush: makeCurrent() failed
qt.qpa.backingstore: composeAndFlush: makeCurrent() failed
qt.qpa.backingstore: composeAndFlush: makeCurrent() failed
qt.qpa.backingstore: composeAndFlush: makeCurrent() failed
qt.qpa.backingstore: composeAndFlush: makeCurrent() failed
qt.qpa.backingstore: composeAndFlush: makeCurrent() failed
qt.qpa.backingstore: composeAndFlush: makeCurrent() failed
qt.qpa.backingstore: composeAndFlush: makeCurrent() failed
qt.qpa.backingstore: composeAndFlush: makeCurrent() failed
qt.qpa.backingstore: composeAndFlush: makeCurrent() failed
qt.qpa.backingstore: composeAndFlush: makeCurrent() failed
qt.qpa.backingstore: composeAndFlush: makeCurrent() failed
qt.qpa.backingstore: composeAndFlush: makeCurrent() failed
qt.qpa.backingstore: composeAndFlush: makeCurrent() failed
...

Is there anything I can do to help debug this issue? I'm currently running the pre-built COPR build, but I think it shouldn't be a problem to compile it directly.

Thanks