Comment # 1 on bug 1216027 from Frank Krüger

(In reply to Jochen Hess from comment #0)
> Since some rolling update within the last six weeks Firefox started using
> the wrongs file chooser dialog for downloads again. 
> 
> I tried starting firefox with the environment variable "GTK_USE_PORTAL=1" as
> many comments suggested but it doesn't work. 
> 
> This worked before fine and changed recently.

Works fine here for TW20231006 with KDE Plasma 5.27.8, Frameworks 5.110, X11,
and FF 118.0.1. Are you using Wayland? Does setting
"widget.use-xdg-desktop-portal.file-picker" to 1 in about:config solve the
issue?