Firefox does not use KDE window decorations and cursor

I installed NixOS choosing Plasma (KDE) and then activated Wayland and installed firefox-wayland. Firefox is not properly integrated into KDE:

  1. Windows decorations are from Gnome (GTK?) and not KDE
    image

  2. The mouse cursor does not scale and looks different over Firefox windows. I am using a 200% scaling and the cursor changes to the small, unscaled, size. The cursor becomes tiny and hard to see. It also does not use the KDE style

    Outside of Firefox window:
    image

    Inside Firefox window:
    image

I checked the Wiki pages for Firefox and KDE and applied the Wayland settings suggested in the Firefox page but it did not resolve my issues.

How can I make Firefox use KDE window decorations and the normal KDE cursor with scaling?

Enabling dconf worked for me.

programs.dconf.enable = true;

programs.dconf.enable = true;

This had no visible effect on my installation.

In the meantime I had extended my configuration and my cursor size problem was resolved. I don’t know what solved it though. The theming problem persists.

In case anyone is trying to get the KDE/Qt file picker in Firefox, you need to following expression in your configuration.nix.

  programs.firefox = {                  
    enable = true;
    preferences = {
    "widget.use-xdg-desktop-portal.file-picker" = 1;
    "widget.use-xdg-desktop-portal.mime-handler" = 1;
    };
  };

Source for why these two options.

Isn’t there a qt extension for FF to make it use the theme? I think I saw one but don’t use KDE so can’t test it.

I am also interested in this problem
Other distros (Debian-based, Fedora, Arch…) have a gtk3-nocsd package that fixes the window decorations, but Nix doesn’t (and given the dependency model of Nix it may not be trivial)
Any ideas ?

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I’m also having this issue. Did you solve it?