Store preferences in device protected storage, which is available before
the device is unlocked.
The keyboard was crashing when trying to access the encrypted
preferences.
The emoji pane uses a separate preferences file, the old data is lost.
The SettingsActivity can't easily use the new preferences storage.
Instead, it continues to use the "default" preferences store, which is
copied back to the protected storage when needed.
There seems to be no "DayNight" theme compatible with older version of
android outside of the androidx library.
Using 'Theme.DeviceDefault' which is a dark theme, even if it doesn't
sounds like. Detect if a light theme should be used at activity
creation.