Well, there are signing extensions like Alby and nos2x, and there is nsec.app which uses a "bunker". They take away the need to enter an nsec (which is dangerous because it only takes one oopsie to a scam site and your nostr "account" is compromised. Some links: http://nostrwiki.crrdlx.infinityfreeapp.com/doku.php?id=wiki:nostr-extension