I just don't see a meaningful integration. There's too much incongruity. The keys are ephemeral and exist only in the user's client, so there's no central mechanism to obtain and exchange keys. Nostr's key system with nsec and npub wouldn't have any relevance in the SimpleX key exchange or chat process. Because again, nostr keys are permanent user identities, and SimpleX exclusively uses ephemeral, local keys. It would be like trying to connect your Blu-ray player to a ham sandwich.