I have just published the following article, which explains how to do an automated Nextcloud install on the Pi (Stretch or Jessie). In three commands, it installs the latest version of Nextcloud and all the necessary packages (using Ansible).
For the moment it is SQLite only.
We also provide the nextcloud-pi-images which are supposed to work (more or less) out-of-the box and provide all important configuration steps (also set up of SSL certificates etc.). If that is something that suits you, you should perhaps have a look at it and help to improve it:
I am aware of nextcloudpi, and am sure it is an excellent image, but I don’t want to contribute to the project at the moment, thank you.