It’s not ideal, but my Load Images AppleScript for Apple’s Mail.app for macOS is updated for macOS 12.x (“Monterey”).
UI scripting is inherently fragile. The many combinations of UI settings and privacy settings make this script really hard to fully generalize. (In US English alone I think there are at least four different combinations, and possibly as many as a dozen? It’s hard to know.) This is probably the last update I’ll bother to publish, unless I figure out something much more clever for making it work.
It would be really nice if Apple took the 60 seconds it requires to add a keyboard shortcut for this command. (Well, I suppose it would take them an hour to do it in such a way that it handled different UI preferences and user locales.)