I believe Nostore is for Safari only (like signing zap.stream messages). But it cant sign a Damus message for example. Right?

Nostore works only in the Safari browser as an extension. The Nostur client app has a built in signing tool though. You have to manually copy/paste an event json into the signer. How does Amber work? Would be cool if that could be a little more automated.

Screenshot of the what the Nostur signer looks like.

Thanks.

You don't have to copy anything. It's automatic. Though the app does have to be open and running in the background. In the future it will have a system service that runs I believe that I read.