Open with/URI handler(?) dialog box no longer shows

Opening PDFs from within a flatpak app like Firefox no longer asks in which app to open, which used to be Okular or LibreOffice Draw. But now it no longer asks and skips straight to LO Draw.

  1. how can I reset this behavior to make it present me options again?
  2. how can I prevent it autoselecting any one app for a particular URI?