Per Setting an incoming e-mail address for the staff group it’s not possible to enable incoming email for an automatic group. This is also something that is not made explicit: for automatic groups the incoming email input is simply not present, leading to confusion for admins.
TBH I don’t see a good reason for this. Having to set up a second group and sync the members to it can be done but is cumbersome and, IMO, unnecessary.
Apart from the ability to email staff this can also lead to new use cases like a TL3 group that can receive emails.
Yes, it’s blocked in the update controller method only.
And I appreciate the workaround, but I don’t think it’s more than a workaround.
Running a Rails command requires someone to be a technical administrator, while doing it in the web interface can be done by a functional administrator. Often these kind of workarounds are presented as a solution (not by you @moin) but they are not, and they are putting off many people using Discourse.