Problem with GTK2 theme

[mauromol]

I recently installed Kubuntu 20.04. After some weeks of perfect working, suddenly (possibly after a Plasma or X crash, but I'm not that sure any more) theme to GTK-2 applications is no longer applied.

First of all: where has the GTK2/GTK3 theme configuration page gone? In my previous Linux Mint 18.3 KDE installation (based on Ubuntu 16.04) I had that page in the Appearance configuration page. Now I only see a "Global Theme" configuration page that seems to allow to change the theme as a whole and not in a selective mode (QT applications, GTK3 applications, GTK2 applications, etc.). Is this by design?

Secondly: after I try to change the global theme, for instance to Breeze Dark, than back to Kubuntu, sometimes the GTK2 theme problem is fixed, but after a reboot I may see again no theme applied to those applications. So it doesn't seem to be a reliable solution and, in any case, it would be nice to understand what happened all of a sudden...

I also posted a question on askubuntu.org for this, but without great success: https://askubuntu.com/questions/1282...x-plasma-crash

Any help would be much appreciated.

P.S.: applications where I see this problem (they look ugly now): Linphone (installed from official repo), Transmission Remote GUI (transgui, installed from official repo), Cisco Any Connect VPN client (installed with its proprietary installer).

[mauromol]

Seems like I've found where the GTK2/GTK3 theme settings has been moved thanks to: https://askubuntu.com/a/1212082/531643
Now I've set Breeze theme for GTK2 applications, previously it was blank. Very strange.
That setting now survived a reboot, I will see whether it lasts or not...

[claydoh]

Glad you found the solution quicklky!
Most of us here are probably still asleep lol.

[mauromol]

Thank you claydoh! I hope I really found the solution, I'll see in the following days, because it's strange that my GTK2 setting was getting "lost" sometimes, I did not play with that setting (especially because I didn't know where it was! :-D).

Do you know about any known cause that could lead to such a behaviour?

[jlittle]

Generally speaking, GTK2 is now unmaintained, and is slowly falling apart. And the GTK3 folks really don't like theming, because it messes up their "brand" and other distinctly non-free ideas; it seems like they've actively jerked around the big theming projects like qtcurve driving them away (though wouldn't expect them to admit it).