Morning NTD , hope you had a good weekend.
Email is currently not being offered for an additional method for a few reasons.
It is much less secure, more prone to errors and has been used incorrectly by many people.
Email addresses are easier to gain access to, and once someone has access to the email they can then receive 2FA codes. Emails themselves can also be intercepted along their delivery chain.
They are prone to errors due to things like having the emails moved to a junk or spam folder, some legacy emails like hotmail can have trouble with sending or receiving.
And one of the biggest ones is that emails are commonly shared among businesses. If a company had a generic 'reception@business.com' email that was accessed by multiple staff then an individual persons 2FA code going to an email that multiple people have access to is not secure.
Authenticator apps and SMS help to reduce any concerns around shared logins and also provide a more secure option for receiving 2FA.
I believe there are options for having a desktop authenticator app, this might be something you could look into as an alternative.
Thanks, Mike