[Mail] Support OAuth for generic mail

Currently when adding an account from a well known provider that supports oauth/saml this authentication method will be used while when using generic/nextcloud accounts the username/password method is forced.

Is it at all possible to also allow private accounts the use of such authentication mechanisms?
I’d like to use OAUTHBEARER as authentication method for my mailservers and SAML for nextcloud but if one of my devices doesn’t support that it becomes difficult.