Nextcloud on Ubuntu 18.04: Admin setup fails

Hi,

I installed nextcloud 9.0.51 via snap on Ubuntu 18.04.
I get to the webpage for admin setup ok.
When I enter all values, the pages takes a while, then a blank page is displayed.
I can verify that in mysql the database was created.
When I got to the nextcloud site, I am presented with the admin setup page again.

My understanding is, that this is not normal behavior. What to do?

Best,

YeOldHinnerk

Latest version is NC 18.04