Keychat currently only supports Nostr Zaps (NIP-57). Its built-in Cashu wallet doesn’t yet support direct Lightning address transfers, so that feature still needs to be developed.
Discussion
Ah I see. That's why I didn't use the word zaps, but said lightning tips in the OP, as it's not a full zaps setup. I'll look into making this use zaps instead.
We will also support Lightning tips. Zaps allow donors to choose whether to display their social ID, whereas Lightning tips tend to be anonymous.