What a neat fireplace! Were you told it wasn't safe to use?

If you do an insert, you can have a black plate made to fill in the rest of the arch. You gotta keep the arch!

If you want to use it, find out why they said it wasn’t usable as a wood-burning fireplace.

A long time ago, I was able to get a gas log set for a wood-burning fireplace insert. I think they just needed a hole to feed the gas line through, although you should ask the pro who installs the gas log set what else may be needed to operate it safely. The insert/fireplace box did have vents, but there were inserts/fireplace boxes that didn’t have vents too. (You should ask if vents are needed. I just got the vented version because I wanted a fan, which I later regretted.) The gas log set didn’t need its own special insert. I only got the insert/fireplace box because there was no fireplace there before - they built out the metal flue and chimney with studs and siding. It was 6’ above ground level.

The gas log set was just set up inside the wood burning fireplace box. The gas log set was a grate, ceramic logs, sand, embers, a gas source and a knob/switch and the thing that made the pilot light stay on. (As far as I could tell. There may have been more components, but it didn’t need a special surrounding insert box.)

Building codes may have changed since then. Ask a local expert. There are other options for non-venting fireplaces like ethanol. I would try to visit a fireplace store that has lots of options on display.

There is a brick fireplace in the house I have now, and it looks like a gas line was put in at some point. There is no gas source now, but the line is still outside. We have no plans to use the fireplace, so I am planning to clean it up and put some fresh logs in there for decoration, maybe with a pretty grate. I can put candles or lanterns on the hearth for ambiance. (Some people like to put a fireplace candleabra inside the fireplace - Crate and Barrel had some nice ones.)

We seem to have the same brick and mantel. Weird.

If you don’t like the inside of the box for some reason, there are cleaning products on Amazon that got good reviews, I think. There are probably other things you can do too.