It will probably come off easily. It does not look like original design.
Now where are you going to put your TV?

TV is being replaced, but it will be mounted on the wall next to the fireplace. I'm ready to use the fireplace for decorating. This was just a temporary solution.

I would get rid of the mantle in a jiffy.

It's probably attached via nails or screws into hidden bracket that has been attached to the face of the fireplace brick. If you Google floating fireplace mantels you will get the idea of how it's usually done. It might be difficult to remove without damaging the mantel, though.

Remove the brass surround (and the TV) and see how the mantle looks.

To me, the mantle looks too big for the space. It might have been added with some easy to remove brackets or more might be complicated.

youTube - search remove a fireplace mantle.

This short one has no audio but it shows how easy it might be. If you are lucky.

https://youtu.be/AfywZhtQZ4g

I also would remove that mantel ASAP. It does not belong on that fireplace. It’s both too wide and too tall.

Thanks everyone this has helped me alot!