How to force old search behavior in GTK3 file dialog

Idealist developers of GTK3 are ruining even the very basic features of the toolkit because they think that changing something from good to worse can be presented as an innovation.

What you can still do is to TAB twice to the file list (press TAB twice right after the file dialog has opened) and start typing. You will have a search dialog in the bottom-right corner displaying what's being typed.