How do I stop counter surfing when nothing seems to work?

Hi all. Otto does not counter surf, but a friend of mine is at her wit's end with her three-year-old Malinois mix and asked me to post here on her behalf because she does not use forums.

She has tried 'leave it', she has tried management (blocking the kitchen), she has tried booby traps with empty cans, even went through a few sessions with a purely positive trainer who basically told her to just never leave food out. Which, yes, fine in theory, but that is not a realistic long-term solution.

The dog is high drive, working-line type, and I suspect boredom and under-stimulation are part of the problem. But even on days with a long Spaziergang and a solid training session, the behavior persists when she steps out of the room.

For those of you who have actually resolved this, not just managed it permanently, what finally worked? Specifically curious whether anyone used a remote collar or boundary training with real consequences.