What framework are you using?
SSO is a solved problem in most frameworks and should be easy to implement quickly.
Rails or Laravel it's quick to implement SSO for various flavors.
Of course, many established companies offer SSO, ability to login using Google, Apple, other oauth.
I asked around to my test users and a few potential users and they mentioned email is fine. In my own experience as a SWE I used many softwares at work which used just email login. However, many more offered a bunch more.
Will it be fine to open it up to broader audience without all these things?