Installation on Ubuntu18.04: pages show menue and tab names, but no data at all

[jost47]

after installation of v0.9 as described, and configuration as described, I'm a bit lost now:
no data is shown on the resulting web pages, and I get no error messages.
Tried to set "error_reporting(1)" in index.php, too, but no messages in the log files either.
Running on nginx 1.14.1, PHP 7.2.10
Any ideas, or anybody with similar issue? Thx at lot!