Maybe we can move this to howto, as still questions about that appear. Or ah, I will collect all information here and write some howto the next hour. About symlink, which seems to be an easy alternative solution: How the enable symlink support for webservers or be sure that they’re supported?
€: Okay for apache it’s simply:
<Directory /> ... Options +FollowSymlinks ... </Directory>
as given in the recommended nextcloud.conf.
Is there something that needs to be done for nginx?
€: Howto done: HowTo: Change / Move data directory after installation
Input/Fixes welcome, and I will add the steps for mysql later and perhaps steps for nginx and other databases.