Tor browser routes all traffic through Tor which is like a super VPN (more server hops and no payment details linked). Downside is that it's slower than VPNs.
KeepassXC just stores whatever you want in text. For my Nostr npub and nsec I created an entry in KeePass called "Nostr Daedalus" then put my npub in the username field and nsec in the password.