Some Erigon nodes run with pruning enabled. You can't tell which ones those are, or how much pruning.

Technically you can tell which Geth nodes are archive nodes with a GetNodeData query over devp2p, although that call is deprecated and will eventually be removed. Its replacement, GetTrieNodes, cannot be used for this.

Erigon nodes are full archival by default, and dont use much space, about 1.7TB, which is quite thrifty consider geth uses like 10TB.

So, many people run full archive nodes now. Thanks erigon team!