Login with username and password instead of email address/SSO

We have a number of employees (as I'm sure a lot of businesses in industries such as manufacturing do) who do not have a business email address.

It would be great if we could have the option to provide a username and password for those employees so they can still access the self service system for things like holiday requests, checking documents, completing performance reviews. It would also allow access during the onboarding process even for those employees who will then later have a business email address and be able to use SSO.

It's not best practice to require employees to use a personal email address for work related tasks such as these and it's inefficient to have a system that only some employees can fully utilise.