made a thing: Signet - a native remote signer for nostr. your key lives encrypted (NIP-49) inside a small daemon on your machine. apps request signatures over NIP-46, and every single request waits for an explicit approve/deny in a native macOS app. the key never enters the GUI, let alone a client. works over public relays, including ones behind NIP-42 auth. 
GitHub
GitHub - zig-nostr/notary: A native signer for Nostr. Your key stays on your machine.
A native signer for Nostr. Your key stays on your machine. - zig-nostr/notary