David Marcus (raised $175M for his LN startup) mentioned Nostr and @jack by passing in his interview in Decoder podcast.
"Bitcoin is still the future of payments". Interesting read.
“I think there might be really good use cases for native Sats-denominated payments, and so if you spend time on Nostr, which is this decentralized social network running on relays."
Check it out https://www.theverge.com/23696466/bitcoin-crypto-lightning-network-lightspark-ceo-david-marcus