Level, anchored into solid studs, and tested before I leave. Evenings and weekends, usually within a couple of days.
Plenty of houses up here have a stone or brick fireplace as the natural TV wall. It is doable and I do it, but it takes masonry anchors and more time, so those jobs are quoted on site. Send me a photo and I can usually give you a number over the phone.
Because I am insured, I show up when I said I would, and I have spent years doing measured installation work professionally. A TV that comes off the wall is not a cheap mistake.
You can supply it or I can pick one up. If you are buying, get a mount rated well above your TV's weight and tell me the model when you book.
I tidy them into a paintable surface raceway or a cable sleeve that runs down to your console. It looks clean and it does not involve cutting into your drywall. If you want cables run inside the wall, that is a job for a low-voltage contractor and I am happy to point you toward one.
Usually within two or three days. I do this work evenings, so a weeknight after work is often easiest for both of us.

Mounted into studs, leveled, and tested before I leave.