wss://relay.jellyfish.land is the first relay ever to use the banner property in its NIP-11.
Discussion
Oh? 👀
As far as I can tell, I generate deltas for relay metrics and the only relay (dead or alive) who I've caught with a banner is this one. I'm still not tracking i2p and tor yet, so maybe one of those had a banner first, but can't say for sure.
