The login page has a Forgot your username link.
Click it, enter the email address on the account, and Yaalago emails the username back to you. The confirmation message is the same whatever you type, so the page never reveals which email addresses belong to an account.
The email arrives in the same branded format as your other Yaalago credential emails and reads well on a phone. It sits next to Forgot password on the login form, so whichever half of your sign-in you are missing, you can get it back yourself.