Currently you can get a user's default timeZone in the user's mailboxSettings. This requires at least MailboxSettings.Read scope. We would like to be able to get the user's preferred timezone back as a property in the user resource, which could use a User.Read scope.
rational: In the current world of hybrid work, a users timeZone is an integral part of a users information, and as such should not require an additional web request and an additional scope to get that info.