Your fireplace hearth goes deep down into the ground and sits on it's own foundation because it really heavy. It weighs a lot, tons and tons. When you finally get it out you'll have a lot of fixing to do.

And still need to put something in its place for a finished hearth as the vinyl flooring cannot run right up to the fireplace as it will melt.

Ditto on that comment, if you keep the wood burning function for the masonry built fireplace you have to have a non-combustible hearth extension. A gas insert would likely have similar dimensional requirements, only an electric (non-heat producing) would eliminate a hearth extension.

Why would you want to replace an expensive masonry hearth with vinyl to begin with ?

Closing it off and putting drywall around it. Its not able to be used

My hearth goes all the way down under my crawl space, on to a cement slab, so yes, it is a big deal. In my case, the fireplace itself goes all the way down to that cement slab also. It looks like you have been tearing it all apart, and the best option would have been to leave it alone, and make it pretty. You could put electric logs in it, even if it is unusable for wood. Even unusable ones look nice in a house.

We had a raised hearth. We took it out because it was massive and took up a lot of space and jutted out into our small living room( fireplace was too large for tiny den)We removed the top layers until we could make a piece of plywood flush with the surrounding subfloor. We removed a little of the surrounding subfloor also to nail plywood covering the hearth area to the floor joist.Then we put engineered hardwood up to our fireplace( it was converted to a non-vented gas log. We don’t use it very much). It looks good.

Thank you for all the comments and suggestions. The way this room is layed out there is only 1 wall that will fit 75" television and only 1 spot to fit the couch right where the fireplace is. The other walls have doorways(front door and entrance to kitchen) in the middle of them making them unable to be used . So bye bye fire place. Have made final decision to drywall it in leaving the mantle as a shelf , so we don't have to take out fireplace. Will post picture when complete. So back to removing the hearth today.Thank you again and any if you have any more thoughts or ideas please continue to comment.

From the pictures I cannot tell what type of structure you have, whether slab on grade or wood framing with a crawl/basement. But yes typically a mortared heavy hearth extension will have it's own framing within a wood structure, or be built directly onto the footing that a slab pours up against, it just depends on what's there. I don't think there is anything difficult in raising the floor to meet the surrounding floor if you remove the hearth. You may also want to seal the flue at the chimney cap.

Here's the before picture

I was thinking this was a non-standard fireplace built in an old house that maybe caused other issues with circulation flow or something (like a 1700's house used for heating in the middle of the kitchen or something like that) so a few decisions led to removing it beyond just a huge tv. But apparently this is a normal god-fearing, corn-fed, red-white-and-blue setup of a nice looking FP between windows. So not understanding leaving the mantel yet demo'ing the hearth - the tv will have to levitate beyond the mantel. Look up tv heights based on your seating position, it shouldn't (nor probably fits) above the mantel.

You should have just built out a full bumpout from floor to ceiling between the windows which hides the FP completely, and left the mantel and hearth behind with a cabinet/table/shelf buildout hiding the hearth. This would allow any tv to have an unhindered wall to be installed at the correct height, hide any cords/receptacles, and have a shelf for any peripheral equipment, yet be removable in the future.