If memory serves me correctly, i was previously able to get people set up with provisioning profile by sending them to an expo hosted page where there was a link to download the provisioning profile and instructions on how to install it.
Update: I found the page I was looking for
I was only able to find this link by googling “expo add devices”, it was the third result. It might be useful to add a link to this in the documentation on somewhere within the dashboard.
Thanks for all the brilliant work,
Rowan