How do you safely defrost a whole lamb? Some supermarkets sell a whole lamb.

The food safety rules for meat dictate defrosting in the fridge, never at room temperature.
The next-size down, a turkey, doesn't even take 24 hours to defrost. It takes either 48 or, if very large, 72 hours to defrost.
How do you reconcile these two rules? In other words, how do you defrost a whole lamb before cooking it?

Is this meant for chefs who have a fridge that will fit a lamb?
Are folks meant to start roasting it while it's frozen? I doubt it would cook through, no matter how gentle the fire.
Do birds (turkey, ..) require special attention because they spoil particularly rapidly, and for a lamb one would get away with defrosting at room temperature? Would 24 hours do it? Would that be actually safe?

I suppose if it's October or March, then defrosting outside in some regions at +5C might work, except that the temperature outside is never constant, which doesn't help much (with either defrosting or with food safety), and that you'd have to stand guard overnight to make sure no other wild animal discovers what feast is ready for them.
Food safety rules are written around the ways bacteria reproduce, not around the chefs' convenience. There is no difference in the speed of getting unsafe between different types of meat (or any other type of non-shelf-stable food). Yes, the lamb is also meant to be defrosted in the fridge. And cooking from frozen is indeed not an option.
So yes, you are meant to defrost it in the fridge. You could do it whole, or you could remove parts of it while still frozen and defrost these, then cook, while the rest stays in the freezer. If you don't have the equipment to do either of that, then your kitchen is simply not ready to deal with buying a whole lamb.
I don't doubt that there are many people who buy it and defrost it outside of the fridge, they just either don't know the food safety rules or make the decision to not follow them.