Some possible ideas:
- Install Echo on loginwiki and rely on cross-wiki notifications. (This might be problematic since we don't want people to actually visit loginwiki.)
- Modify LoginNotify to send notifications to a user's home wiki (as defined by CentralAuth) rather than the local wiki.
- Modify LoginNotify to send notifications to a configured fall-back wiki (e.g. meta) if Echo isn't available on the local wiki.
- Disable login at loginwiki
See T153335#2899401 for more discussion.