Well, some of the foods at chains like that are made by either their own food factory, or under contract to a company that does it. I can't tell you what chains and what foods in specific because it's been too long since I discovered this.

But, it means that you've got a couple of options.

The most realistic is you just hope that the chain sells their stuff in grocery stores. Some do. Iirc, tgif sells a goodly number of its appetizers that way. I wanna say Applebees does too, but I don't really pay attention to that section of the freezer aisle.

Less realistic, but not impossible, is to check at the restaurant. Some of them will actually sell the products like that. It's pretty rare, and you'll pay the full retail price, but you can then take it home and heat it up yourself.

And, sometimes, you'll find employees stealing the stuff and selling it. No bullshit, it happens. Happens in fast food as well, for that matter. Used to know a guy that would take requests from burger king. You catch him on the right day, you could get a giant box of the whopper patties for twenty bucks. He'd just pad the waste reports over a few days, and afaik, nobody ever caught on.

But, yeah, pre cooked chain restaurant food is usually produced in bulk at a factory, same as your typical frozen foods ata grocery store. Just with bigger packages. Have a cousin that used to work at one, though I can't remember which chain it was.