Turns out it was not disabled, just changed. No longer activated through double-click, but through single-click, and has new shiny graphical elements. The change just happened to break image frames created under the old system, or at least ones that are on master pages. A new image frame created will function normally.
Likely you are aware, but if not: in the latest beta, 293, double-clicking on an image no longer activates the interface allowing scaling and rotating of the image within the picture frame. Using Windows 10. A feature thought in this area: it would be very great, and for many projects crucial, to be able to both get and change this information (exact scaling and rotation angle) in a dialog box.