The GTK settings daemon failed to load the default theme (e.g., Adwaita or Windows 10-style). This is common in version 2414 if the GSETTINGS_BACKEND is misconfigured.

Error: Gdk-DirectDraw-Critical / Vulkan Initialization Failures

Or manually set:

When software is developed using cross-platform GUI libraries like GTK+, the application itself doesn't contain all the visual components needed to draw buttons, menus, and text fields. Instead, it relies on a "runtime environment" installed on the host system to interpret these graphical instructions.

While the tech world has moved toward GTK 3 and GTK 4, version 2.24.14 remains highly relevant for maintaining and running stable legacy applications. What is the GTK Runtime Environment?