Admin panel localhost only


I found this post about localhost-only admin panel, but wondering if there has been any expertise since this was written to restrict it to localhost only?

Preference would be to allow roundcube access to world still, but if not, happy to try localhost binding of nginx, and then use apache as a proxy to nginx roundcube.

Any ideas would be helpful, I’m not much of an nginx user - but will check out in next week or so as time permits to play around with it.