I’ve switched to storing an encrypted version of my private key and copy that around instead the raw private key or nsec

https://github.com/nostr-protocol/nips/blob/master/49.md

You can use nak to encrypt your private key.

https://github.com/fiatjaf/nak?tab=readme-ov-file#encrypt-key-with-nip-49

For login, I usually use nip-07, nsec.app, Amber, or run my own bunker using nak.