Have done a fresh installation of Kubuntu 20.04.1 about a week ago. Basically, everything KDE or QT related works okay, but Claws Mail doesn't. The problem is the same as that described at https://www.thewildbeast.co.uk/claws-ma ... id=4105#c0 ..

After clicking in message body or list or anywhere outside the input of selected text, the text shows as white color on white background which makes it "disappear".

This happens in other fields/boxes as well, like the 'From' and 'To', etc fields.

The themes that come with Kubuntu do not work with Claws, which uses GTK+ 2.24.32 / GLib 2.64.3

There was a theme suggested called "Gilouche" but that is 14 years old it seems. Any theme suggestions please ?

Have installed the "Adwaita" theme and the problem is solved. As 90% of the applications I use are KDE/Qt based, I had to leave the Theme at a system level as it was. As this problem was only for one Gnome/GTK based application, the "Adwaita" theme was only applied as follows:

System Settings | Application Style | Configure GNOME/GTK application style | then set it for GTK2 and GTK3