Enable a fully anonymous registration without email requirement. As searching the web is a very privacy related topic and Kagi claiming to be a privacy focused search engine, user should have the possibility to register fully anonymously. Yes, an anonymous email can be used for registration so far, but it will always be linked to you in some way.
An ideal example for an anonymous registration would be Mullvad. Upon registration a user account receives a preset account ID (a 16 digit random number) which cannot be changed. Im not sure how practicable this would be for Kagi.
Another good option would be a registration like IVPN. The user can choose between standard email registration or using a generated alphanumerical code. I think this might be the way to go, as Kagi could please both type of users: the ones who would like to maintain a link between their Kagi account and their email. And the ones who would like to use Kagi fully anonymous.
Using a login number à la Mullvad or IVPN also doesn’t require any password. As Kagi doesn’t hold any personal data, that is not a security issue in my opinion.
The last method I can think of, but my least favorite one, would be something like choosing a username + password (instead of email).
I would love to read some more ideas on this topic.