That varied by state, usually at the whim of whoever the governor was. Some like Florida and South Dakota remained open with no restrictions. In North Carolina, the very first lockdown was the restaurants, which were closed by executive order of the governor except as to drive through or takeout and many of them were not set up for that. Even those that were, it tanked revenue. It was tough on the restaurant business until they were allowed to reopen. Your state may have been more fortunate, but many were not.
This may be a matter of semantics. We, as individuals were not locked down where we could not go out, but the restaurants were locked down where they could not let us in, and that put them in a bad way, businesswise.
I never think of chain restaurants when I think of seafood. On the Outer Banks there are several local favorites that have been there for decades. When we use our summer timeshare weeks there, we always head to Sam 'n Ommies in Nags Head and Darryls in Manteo. If I am doing a trip to the Crystal Coast, it is the Sanitary Seafood Restaurant in Morehead City which predates World War II. These restaurants offer a lot of fresh local seafood, as well as some frozen. If we are visiting my brother below Wilmington, it is one of the cluster of seafood restaurants at Calabash, NC. Closer to home, if we want seafood, we drive over to Winterville to the Dixie Queen which has again, been there for decades. There is a Red Lobster in Greenville, the next town north of Winterville, but I have always wondered how they survived with the Dixie Queen just down the road.