After much blood, sweat and tears, I have pushed Mautic 3 update now. It's a major update, so you have to manually click the update button in the dashboard to update (i.e it won't automatically update).
Let us know if you hit any issues.
Finally, though we had to put in lots of packaging effort on our side, the real hero is madmath03. I don't really know him (nor did we work together on this) but he did a lot of work to get the CLI working and the LDAP plugin functional in the mautic code base.