Those missing icons are app icons.
For instance, gnome-calculator's app icon according to its .desktop file is now "org.gnome.Calculator"
A monochrome icon is show in GNOME Shell's top bar when calculator is running.
Which suggests this workaround:
sudo cp /usr/share/icons/Yaru/scalable/apps/org.gnome.Calculator-symbolic.svg /usr/share/icons/HighContrast/scalable/apps/
sudo update-icon-caches /usr/share/icons/HighContrast
Perhaps GNOME Shell should look for -symbolic icons when the theme is set to HighContrast?
Those missing icons are app icons.
For instance, gnome-calculator's app icon according to its .desktop file is now "org.gnome. Calculator"
A monochrome icon is show in GNOME Shell's top bar when calculator is running.
Which suggests this workaround:
sudo cp /usr/share/ icons/Yaru/ scalable/ apps/org. gnome.Calculato r-symbolic. svg /usr/share/ icons/HighContr ast/scalable/ apps/
sudo update-icon-caches /usr/share/ icons/HighContr ast
Perhaps GNOME Shell should look for -symbolic icons when the theme is set to HighContrast?