I've been playing with @Keychat and it's a really cool messaging app. Unlike some other nostr messengers, Keychat isn't yet another nostr client with messaging capabilities. It's a purpose-built, dedicated, private messaging app built on the Signal protocol, and nostr to provide a seamless, secure messaging experience. It also has integrated Cashu (eCash) for sending and receiving sats in-app. I highly recommend downloading it and giving it a try!
