Depends on whether you are on Android or iOS. I think there is a signer extension for iOS, but I don't keep up with Nostr development on Apple devices, since I don't own any.

If you are on Android, you should be able to get Alby or Nos2X signing extensions for Kiwi Browser and be able to log in that way, without having to put in your nsec.

We need NIP-46 login on zap.stream, though. Then you could use Amber.