I've found a few interesting nodes.
Here's one without any Tor or IPv4/IPv6 address to connect to: https://amboss.space/node/03ecd3e00d2a32bc8e550b81f98f58956492118d5cc930c71073f6b8790d1ef0b7
Here's a node with a 127.0.0.1 (localhost) address:
https://amboss.space/node/0201be5b63e839fc57c66c7ab21dcea3aa79001de132f29ade96a0c2d6680c8eaf
At time of writing, both nodes have at least one public open channel, and they appear to be online (last_update is within 24hrs).
Is this a bug? How did these updates get propagated by LN Gossip? How do their channel peers communicate? How are these nodes able to communicate with the rest of the LN without any public connection address posted?