How do I disable the file type filter in KDE's file picker?

cross-posted from: https://sh.itjust.works/post/54871719

When I open a "Save" dialog, or a file selection dialog, only one type of file is shown. Sometimes it even filters by the extensions.

I don't want this! This isn't Windows, where file extensions really matter! How do I disable the filtering, or set it to show "All Files" by default?

The "Save Page" dialog: you'd think there are only 2 files here, both .html files

Nope! There's lots of stuff!