"No MonoBehavior scripts in the file" despite correct file and class names on Unity Linux 2019.2.3f1

Hi!
I am facing a blocking issue with "No MonoBehavior scripts in the file, or their names do not match the file name" error message when creating a simple HelloWorld project. As it did not work, I created another project named "test" so that there is no possibility of making error with letter cases, still the same.

My components are:
- Ubuntu 19.04
- Unity Linux 2019.2.3f1
- mono --version = Mono JIT compiler version 5.18.0.240

Console is silent. What is it where I could check more detailed error message?

EDIT: it does however work under the same Linux and mono environment with 2017.4.31f1 and 2018.4.8f1 versions.

Regards, eltomek