I wish to change the default Nautilus file dialog that Firefox uses, to Dolphin (my main file manager) but I cannot find any solution. Every single time I download an image, Nautilus is opened instead of Dolphin.

I tried adding GTK_USE_PORTAL=1 to my env variables, and It didn't work, then I tried changing mimetype and also did not work, I also tried modifying the xdg-portal (sorry if I'm wrong) to use xdg-desktop-portal-kde instead, but I cannot accomplish this since I didn't understand at all the Arch wiki and IIRC some files aren't exactly where the Arch wiki was pointing them.

As a last attempt, I open about:config in Firefox and search for widget.use-xdg-desktop-portal and set it to True, and still I keep having that old Nautilus as my file picker in Firefox, and this last thing usually worked well for me in Plasma.

Edit: I just restarted my pc and now randomly seems that Dolphin it's the file dialog for Firefox, I don't have a single clue how this happen.