story
For auth, the core Elixir team has made one prototype but I am not sure if they'll pursue it further. Outside of that, use Pow. For file attachments: Waffle. Authorization: CanCan, although the area has several very solid options, I heard.
Discoverability can indeed be a problem. Covid-19 hit everything pretty heavily and Elixir's community is no exception. Just a month ago people started finally hiring for it again (on the forum).