Anki not picking up GTK theme on Gnome/Linux

You can work around this issue by explicitly telling Anki what the GTK theme is. Run the following commands in a terminal:

theme=$(gsettings get org.gnome.desktop.interface gtk-theme)
echo "gtk-theme-name=$theme" >> ~/.gtkrc-2.0
echo "export GTK2_RC_FILES=$HOME/.gtkrc-2.0" >> ~/.profile

Then log out and log back into your computer, and Anki should pick up the GTK theme.