wekan/client/config/accounts.js

AccountsTemplates.configure({
  confirmPassword: false,
  enablePasswordChange: true,
  sendVerificationEmail: true,
  showForgotPasswordLink: true
});

AccountsTemplates.removeField('password');
AccountsTemplates.removeField('email');
AccountsTemplates.addFields([
  {
    _id: 'username',
    type: 'text',
    displayName: 'username',
    required: true,
    minLength: 5
  },
  {
    _id: 'email',
    type: 'email',
    required: true,
    displayName: 'email',
    re: /.+@(.+){2,}\.(.+){2,}/,
    errStr: 'Invalid email'
  },
  {
    _id: 'password',
    type: 'password',
    placeholder: {
      signUp: 'At least six characters'
    },
    required: true,
    minLength: 6
  }
]);