screensaver unlock dialog is not respecting the application theme set via Gnome-Tweak

Hi there,

I am currently using gnome flashback on top of i3wm in Ubuntu, which has been mostly wonderful. And I have set the application theme to Adwaita.Dark via gnome-tweak.

However since I upgrade to Ubuntu 22.04, the color of screensaver unlock dialog has become the 'ugly grey'.

I am hoping to change the dialog's color to match the rest of the theme, so I can go back to my happy days. I understand it is possible the problem is not from gnome-flashback, but I don't know how to start, and any pointer you can give me will be great.

Thanks in advance for your help!