If you agree, could you file a feature ticket to alter the HTML attributes of the combined username/email field when CB is configured for
Login Method: Email.
The HTML attributes should be:
- type="email" (not "text")
- autocomplete="email" (not "username").
- You might want to consider adding inputmode="email" as well.
Without these, a smartphone doesn't select its email-specific soft keyboard for completing the field, and it doesn't autocomplete the email address.
For my own site, I can edit my template override. But this is a request to fix the more general 'bug' at source.