How to provide user login with a username and NOT an email?

Question

I\'d like to use Firebase for my web app that is for people with dementia in a care home. They do not have email or social network accounts so will need a simple username /

Answer 1

You may use Alfonso's solution as well. And where you need a real e-mail, you can set an textfield for an e-mail when the user registers and you can keep it in your database and you can use it.