Why is the Linux/GTK Implementation of KNIME so extremely bad?

The linux/gtk implementation of the gui is HORRIFYINGLY bad. It has glitches, mindnumbing bugs and looks horrible. Invisible gui elements, non-functioning buttons, quick node selection bugs out every few minutes and worse. We tried multiple ubuntu versions and multiple different themes, all have the same problems. No problems whatsoever when using Win10.

Is Linux not officially supported anymore?

Please consider filing specific reproducible bugs so that they can be fixed.