How to enable system theme for Firefox?

cross-posted from: feddit.de/post/7895009

I’m a semi-recent NixOS user and one thing that bothers me since the beginning is that when I change the Gnome theme (between light and dark), Firefox doesn’t adapt. The system theme in Firefox is enabled, but it always displays the light theme, no matter what theme is selected in Gnome.

Internet search, including searching through NixOS discourse, packages, options and Nixpkgs repo surfaced a solution.

Any ideas or tips how to achieve system theme integration for Firefox on NixOS?

NixOS 23.11 / Gnome 45 / sway