Sure thing. It's been a while and I've only seen a few, but I'll do my best.

So normal lungs are puffy enough, and smooth and glistening on the outside. On the inside, they resemble a kitchen sponge. They are soft and pliable, and able to easily contract and expand to inhale and exhale air.

In these COVID lungs, the outside was very ragged and shaggy. They were distorted with a lot of contracted areas. When you cut into it, there was some residual spongy areas, but a lot of it was white, firm, and solid. Think of how you might get a gnarly scar on your arm from a bit cut. Except instead of just being a single scar, almost the entirely of the lungs are scarred and firm. They aren't able to contract and expand easily anymore because of how firm and rigid they've become. And because they no longer have the spongy architecture, it means many of the airspaces are lost and there is far less areas for potential gas exchange.

So I'm not positive, but I'm fairly sure these COVID lung transplant attempts are primarily performed on younger patients after their body was able to clear the virus. It's just that in these individuals, although they no longer had COVID, the resulting scar tissue absolutely destroyed their lungs. It doesn't happen in every case thankfully...or even most cases, but when it does it's a bit scary.

I remember one of my cases being a young pregnant woman who had to be put on an ECMO machine (artificially oxygenates the blood when your heart and/or lungs cannot). I don't know whatever came of her, but I hoped she was able to go on and lead a relatively normal life.

You can read a bit more about this sort of thing here: https://en.wikipedia.org/wiki/Interstitial_lung_disease