Every app can register a scheme/protocol like https:// to open links inside the app. Nostr apps should open nostr:// links like nostr://note12ang9z42jgtgs95fazm49ektzqec9g2n26hqz82nt6jtyskffczsda3vpz)
Discussion
Thanks. It appears that the link you shared opens up Iris but not in Snort. They're the only two I've checked so far.
Will clients have to agree on a standard?
I don't know any standards for this. But i found some manuals for iOS and Android apps: https://www.google.com/search?q=app+register+link+schemes