In case, like me, you’re finding some GNOME apps continue to have a light colour scheme when the rest of the default desktop is dark - there’s a quick command to resolve that:
gsettings set org.gnome.desktop.interface color-scheme 'prefer-dark'
With that, apps such as Activity Monitor, Tuba and Apostrophe should start to respect the overall look-and-feel for the rest of the desktop.
I submitted a merge request to propose adding these settings to the default user profile, but this is my first time using Gitlab here so let me know if I’m doing it wrong…