I could see them essentially pre-packaging everything (even the fresh stuff). Instead of having a buffet tray with a spoon that everyone uses, they have lets say 3 spoonfuls of mac and cheese already on a plate sealed with plastic wrap (or foil or whatever).
That way everything becomes a single-serve portion and you don't have to worry about sharing the serving spoon. In addition you can visually see if someone has broken the seal into the food.
The other option of course is to remove the "self-service" portion of the buffet and instead put up glass in front of the buffet have staff who work the bar and serve you. Again eliminating the shared serving utensil problem (and the assumption being that all the workers have the daily temperature checks, gloves, masks, etc.).
The second option is what I imagine many hotels who promise hot breakfast will have to if they want to maintain the efficiency of buffet style vs. individual orders.
If DL wanted to be somewhat innovative they could also provide in-app ordering and just have all food remain in the kitchen and you simply order to your seat and it's delivered by someone wearing gloves/masks and the plate again is sealed with plastic so you can visually verify it hasn't been tampered with between kitchen and you. Downside is wait time and losing flexibility to easily get seconds but that could