"Follow device theme" no longer switches to Dark mode automatically

[Cheap-Skate]

Steps to reproduce

Set Customise > Follow device theme
Switch Android phone between Light and Dark mode (aka Night mode)

Expected behavior

Fenix switches to dark mode (it did this until a week or two ago)

Actual behavior

No switch (this new broken behaviour started perhaps 2 weeks ago)

Device information

Galaxy A40, Android 10, today's Fenix Nightly

┆Issue is synchronized with this Jira Task

[ghost]

Yes, this happens on my device too. The dark mode or the light mode don't automatically switch when the dark mode is enabled or disabled System-wide.

Device: Motorola One Power, Android 10.

Fenix Build: Firefox Preview 4.3.0 (Build #21082025)
And
The today's Nightly

[umerf52]

I'm also facing this bug.
OnePlus 3T, Android 10 (LOS 17.1, 20200401)
org.mozilla.fenix.nightly, Nightly 200416 08:30

It's daytime (1:40pm) right now, so everything is in light mode
In Phone Settings > Display > Dark Theme = Will turn on automatically at sunset
Fenix is set to follow system theme, but it is currently following light theme.
All other apps that are supposed to follow light mode are in light theme, e.g. Slack etc

[ygretharekar]

Hello I am able to reproduce the bug on my device, I would like to work on the solution, thanks.

[ekager]

Thanks for bringing this to my attention! I found a fix and should be working after #10074 lands.

[sflorean]

Verified as fixed on Nightly 04/23. Devices: Samsung Galaxy Note10 (Android 10) and Xiaomi Redmi Note 8T (Android 9).