Under default-dark theme, an active frameless GtkToggleButton inside a GtkNotebookPage looks the same as an unactive one
Steps to reproduce
- Select Adwaita-dark in gnome-tweak-manager's Legacy applications setting
- Compile and launch
- Click on the toggle button
The button looks exactly the same regardless of its active state.
There should be a visual change to show the active state, like with the default light theme