It looks like this can be done with groups. These can contain members from outside our Gsuite. By default, groups are accessible to everyone in our Gsuite, not just group members, though this can be changed if necessary.

I've copied all the function addresses from Loopia to Gsuite as a recipient address map. It's disabled until all the other addresses are sorted out. I took the opportunity to change some addresses that were aliases so they forward instead of duplicating the recipient addresses.

The recipient map is now enabled and all the function addresses for @wikimedia.se have been removed from Loopia.

The addresses are handled as recipient maps initially, since that was the easiest way to fix it. Some of them may be more useful to have as collaborative inboxes (see T197864).