To be honest, the concierge lunch in the MDR isn't anything to write home about.
Also, I've cruised on Royal, Princess, Carnival, NCL, and Disney. Royal and Carnival definitely do not have an MDR option for lunch on embarkation day. I believe Princess still does. Not sure about NCL, but there is a sit down venue always available. I also don't recall about DCL. Generally, I tend to board later after lunch in the MDR (if offered) would have already been shut down, so it's not something I've really looked for.