I would be nice if you could enable the option to receive an email alert on successful login.
I support this idea because email notifications will improve NextDNS account security.
In my opinion, account security is crucial because:
1) Hacker who takes over NextDNS account will know user operating system, antivirus, online services, etc. This information will significantly help the hacker to prepare and conduct a successful attack.
2) Hacker can use the rewrites feature (in settings) to redirect the user to a malicious website.
For the same reason, I suggest U2F Security Key (YubiKey) support: