Any idea on what it would take to reno these FPs?

[Warpy]

17. Oooks like a false fireplace

They were put into working class housing in the 1920s-30s so there would be a cheap mantelpiece for the photos and knickknacks but that's all they were. They weren't boarded up because there was no firebox or flue.

The giveaway is the hallway/stairwelll on the other side of the wall.

What you can do with these things is recycle the mantelpiece, either taking it out completely or using it with a prefab firebox on an exterior wall, either for a wood or gas fireplace.

(They thought they were being clever by installing an actual heat source in the false fireplace, go figure)