Yes, I am aware of this, however, if you look at most design, they don't follow this rule and that is where the issue is. Looking for some suggestions. Thought about actually doing a split fireplace (meaning one on either side of the TV) but couldn't find any pictures of something like that.

If you're comfortable with the TV at that height then there's nothing wrong with it, but it's not something I would choose to do. Some people don't really have any other options because of the size of the space they're working with, or the configuration of it. While symmetry can be pleasing, asymmetry can also be interesting. Can you show us a picture of your space? Somebody may be able to come up with a solution you haven't thought of.

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Typically the FP is longer than the TV.

It would be my recommendation that you build a box so the TV is recessed and doesn't extend beyond the face of the wall.

The slimline fireplaces are generally for modern rooms and modern design many times embraces asymmetry. If you have space to the side, I would think it would be a more comfortable viewing height. kandrewspa showed an example that I think is nice. I don't think 40" is terribly high, especially if you're sitting far enough away. If you don't have a modern space, I wouldn't do a slimline fireplace.

Thank you all for your input. Here is a picture of how it CURRENTLY is. It is a lot of wasted space. Our plan is to rip out the entire wall where the fireplace is and build new. We are going for a much more midcentry modern flair. There are 10' ceilings. Want to incorporate more wood tones and organic materials. These are NOT our furnishings. The eventual plan is to replace the flooring with LVP, wider base, Hope this helps.