A review of the Google Keep APK revealed that Google has plans to make an obscure theme available to the annotation app.
Dark mode starts to be released through a server-side update from version 5.19.19. Google Keep's dark mode replaces white with dark gray.
Android's status and navigation bar also match the same tone on Android Q for a consistent look, with the settings page getting the same treatment.
The ?Note List? and ?Quick Capture? home screen widgets are given the same theme to match the main app.
This mode can be enabled in the settings through the option ?Enable dark theme?.