Ethernets.io aims to provide information for node operators, as well as core devs, and researchers.
Node operators to get information about their node, and to see if it's ports are open to the internet so that other nodes can connect to it. You can search for a node here.
For core devs, and researchers, it provides a source of network information, and it doesn't only cover mainnet, it covers all the testnets, and ephemery networks.
We can see trends over time, like changing client diversity, or how quickly new versions of a client are adopted, or fork readiness, useful for those organizing new hard forks.