To steam and froth well, a plant milk needs to:
Have a protein content of at least 2%: Milk increases in volume when steamed because its proteins stretch. If it has very little protein then it won’t stretch when steamed.
Have a fat content of under 2.5%: Fat impedes the ability of proteins to stretch when exposed to heat. This is why skimmed milk can foam up much more than semi-skimmed.
Handle temperatures over 60 Celsius without curdling: Baristas generally steam milk to 60 Celsius and you don’t want your milk to even approach splitting at this point.
Have some sugar in it: Steamed dairy milk is sweet because heat breaks down its lactose into sweeter sucrose. Sweeter plant milks will be closer to steamed dairy in flavour.
The milk that best ticks all these boxes, and is therefore best for frothing and steaming is oat milk. It’s not a coincidence that the majority of coffee shops use oat milk to make their lattes and cappuccinos. Coconut milk can also steam well, however, this has a very strong flavour. A coconut milk latte will taste very different from one made with dairy (or oat) milk. Some people love it, some people hate it.