Canary now lets you pick a theme for the app that’s different from your device’s theme. You can easily change your theme right in Canary Mail:
- Go to Appearance in the settings.
- Select Theme.
- Choose Light or Dark. If you select Automatic, Canary will follow your device's light/dark theme setting.
For further information:
https://canarymail.io/blog/dark-and-light-mode/