How can I make all applications use Nemo's file selection dialog instead of Nautilus?

I switched to nemo a long time ago, because I think it's superior to nautilus in many ways. One small thing bothers me however:

Whenever I want to open a document in gedit (or evince, but I'm sure there are other programs as well) not the nemo file-selection window appears but the nautilus one.

I did of course replace nemo with nautilus as suggested in a lot of other posts:

 gsettings set org.gnome.desktop.background show-desktop-icons false

and

 xdg-mime default nemo.desktop inode/directory application/x-gnome-saved-search

and also did

 ln -s /usr/bin/nemo /usr/local/bin/nautilus

in order to completely replace nautilus, but this doesn't help. Which program/executable is triggered when hitting open (Ctrl+o) in gedit/evince?

It's not a nemo vs nautilus issue. It's a GTK+2 vs GTK+3 issue. Apps written for GTK+2 will use the familiar-looking Humanity-themed file selection dialog, while apps written for GTK+3 will use the alien, hollow-looking default theme for GTK+3.

Unfortunately, the only way to get a consistent UX is to use all GTK+2 apps, or switch to a Qt-based DE like LXQT or KDE.

Sorry.