Setup fails: No content collection

I’m trying to get started with Neos. I followed the installation instructions very carefully but the setup of de Neos Demo site fails. I’m installing Neos of a fresh VM instance of Ubuntu Server 16.04 with php7.2 and apache2.

After submitting the user account information during setup, an error occurs and the setup stops. When I then navigate to the main url the following message is shown:
An exception was thrown while Neos tried to render your page
No content collection of type Neos.Neos:ContentCollection could be found in the current node (/sites/neosdemo) or at the path “main”. You might want to adjust your node type configuration and create the missing child node through the “flow node:repair --node-type Neos.Demo:Homepage” command.
landingPage<Neos.NodeTypes: Page>/
body<Neos.Fusion: Template>/
main<Neos.Neos: PrimaryContent>/
default<Neos.Fusion: Matcher>/
For a full stacktrace, open Data/Logs/Exceptions/20181209231233e06147.txt

Could someone please help me to get this demo site working?
Thank you!