Most Apps conform to Dark Mode in Cinnamon except Gnome Calendar and Contacts! Not a huge issue but as a new user, I’d like to know if this is a common anomaly!
If you’re not using GNOME
If you want to change the theme of Libadwaita applications on another Gtk desktop like Xfce or Cinnamon, you can use the following commands:
Light Adwaita theme:
gsettings set org.gnome.desktop.interface color-scheme default
Dark Adwaita theme:
gsettings set org.gnome.desktop.interface color-scheme prefer-dark
…and welcome to the forum !