I run v8.17.3 on my ipad on iOS 12.1.4. I had to log out of my account and when I went to log back in the welcome screen gives you only two options: Login with Google [Google button] or Create New Account [text box with 'email' greyed out]. If you enter an email into the box, it sends you to the create new account screen and so I apparently have two accounts linked to the same email address now. If you enter your username in the box, it sends you to the regular email login page and you can link to your existing account. But there is no link to login using anything but Google on the home page and you'd have no idea you should enter your username into the text box marked 'email' unless you're just hacking at the fields to try and access your account.