I don't have a tonne of experience in the DL F cabin but I have flown the YYZ-ATL leg in F recently (January). This was an early morning flight. No meal was served. Just drinks and the snack box. It was still a nice experience though.
Luckily, the YYZ-ATL leg is considered "international" so access to the SL is granted. The SL I went to in ATL was busy but still had plenty of seats. The buffet was well stocked but it wasn't really a full meal.
Hopefully someone with much more DL F experience will chime in as well.