It's improved since I last asked it about Nostr, it understands what it is and can attempt to code a web app that shows events from given relays, and it connects to those relays, but it can't successfully subscribe to them even after I point it to protocol docs.

It's likely possible to make it work, but at the time of writing it also seems like more effort than just coding it yourself and having ChatGPT just handle the UX, graphics, and other non-protocol specific stuff.