Now I’m no lawyer (I hope to hire one though … ) but it looks like Mississippi law is gonna disagree with you about “nostr clients”.

I’d wager that their definition of a “digital service”, as one that “collects or processes personal identifying information”, is gonna encompass any Nostr client that sends events to relays. The term “processor” has special legal meaning in this context, as does “controller”.

Nostr’s architecture lends itself well to separation of concern, allowing apps to perform discrete services on behalf of “user controllers”. Because events are signed by user held keys (and thereby “immutable”) relays simply storing events would not be considered controllers or processors. But I’m sure regulators will find other ways to regulate, if they wish.