Someone tried to build an Ethereum-based Nostr client called Dostr.
Among the reasons it failed, IMHO, is why most Ethereum projects fail. It required that users already have an Ethereum wallet to connect in the first place. By tying your social graph to a blockchain, you immediately limit the potential size of your audience to only those who have already self-identified with that subgroup.
Nostr doesn’t use or need a blockchain to function. That’s an important point that the crypto people (I am using a much nicer word than I usually do) often overlook.
https://dostr-eth.github.io/homepage/
