Suggest an alternative to

authy-devise

Authy Devise plugin to add Two-Factor Authentication

Why do you think that https://github.com/castle/ruby-u2f is a good alternative to authy-devise

A URL to the alternative repo (e.g. GitHub, GitLab)

Here you can share your experience with the project you are suggesting or its comparison with authy-devise. Optional.

A valid email to send you a verification link when necessary or log in.